Detection of electric motor short circuits

ABSTRACT

One embodiment describes a method that includes determining a desired torque level of a motor actuated by a motor starter; determining, using a control system, a configuration of the motor starter to achieve the desired torque level, in which determining the configuration includes determining which of a plurality of switching devices in the motor starter should be opened and which should be closed; and instructing, using the control system, the motor starter to implement the determined configuration by opening or closing one or more of the plurality of switching devices.

BACKGROUND

The present disclosure relates generally to switching devices, and moreparticularly to operation and configuration of the switching devices.

Switching devices are generally used throughout industrial, commercial,material handling, process and manufacturing settings, to mention only afew. As used herein, “switching device” is generally intended todescribe any electromechanical switching device, such as mechanicalswitching devices (e.g., a contactor, a relay, air break devices, andcontrolled atmosphere devices) or solid state devices (e.g., asilicon-controlled rectifier (SCR)). More specifically, switchingdevices generally open to disconnect electric power from a load andclose to connect electric power to the load. For example, switchingdevices may connect and disconnect three-phase electric power to anelectric motor. As the switching devices open or close, electric powermay be discharged as an electric arc and/or cause current oscillationsto be supplied to the load, which may result in torque oscillations. Tofacilitate reducing likelihood and/or magnitude of such effects, theswitching devices may be opened and/or closed at specific points on theelectric power waveform. Such carefully timed switching is sometimesreferred to as “point on wave” or “POW” switching. However, the openingand closing of the switching devices are generally non-instantaneous.For example, there may be a slight delay between when the makeinstruction is given and when the switching device actually makes (i.e.,closes). Similarly, there may be a slight delay between when breakinstruction is given and when the switching device actually breaks(i.e., opens).

Accordingly, to facilitate making or breaking at a specific point on theelectric power waveform, it would be beneficial to determine the delay.More specifically, this may include determining when the switchingdevice makes or breaks.

Additionally, since the switching devices may make to supply electricpower to a load, it would be beneficial to determine if there are anyfaults, such as a phase-to-ground short or a phase-to-phase short,before fully connecting electric power to the load. For example, testingfor faults before fully connecting electric power may enable the faultsto be detected while minimizing the peak current and/or let throughenergy resulting from the fault condition.

Furthermore, switching devices may be utilized to provide electric powerto electric motors. For example, in some applications, the switchingdevices may be included in a wye-delta starter or some other motorcontrolling device. As used herein, a “wye-delta starter” is intended todescribe a device that controls operation (e.g., speed, torque, and/orpower consumption) of an electric motor by connecting winding in theelectric motor in a wye configuration, a delta configuration, or a mixedwye-delta configuration. In fact, in addition to controlling starting ofthe electric motor, the wye-delta starter may control operation and evenstopping of the electric motor.

More specifically, the electric motor may be started by connecting thewindings in the motor in a wye configuration to reduce voltage suppliedto the windings, which may also reduce the torque produced by the motor.Once started, the windings in the motor may be connected in a deltaconfiguration to increase the voltage supplied to the windings, whichmay increase the torque produced by the motor. However, as describedabove, opening and closing the switching devices to connect the electricmotor in the wye configuration and to transition from the wyeconfiguration to the delta configuration may discharge electric power(e.g., arcing) and/or cause current oscillations to be supplied to themotor. In some embodiments, reducing the likelihood and magnitude ofelectric arcing and/or current oscillations may increase the lifespan ofthe switching devices.

Accordingly, it would be beneficial to reduce the likelihood andmagnitude of electric arcing and/or currently oscillations produced whenmaking or breaking a switching device. More specifically, this mayinclude opening and/or closing switching devices in the wye-deltastarter at specific points on the electric power waveform.

Moreover, wye-delta starters generally supply electric power to electricmotors to run the motors in wye or delta configuration. Morespecifically, when the motor is run in a wye configuration, the electricmotor may use less electric power and produce a first (e.g., lower)torque level, and when the motor is run in a delta configuration, theelectric motor may use more electric power and produce a second (e.g.,higher) torque level. In other words, running the electric motor with awye-delta starter enables two operating modes (e.g., less powerconsumption lower torque and more power consumption higher torque).However, there may be instances when it is desirable to operate themotor somewhere between the two operating modes. For example, it may bedesirable to produce more torque than produced when operating in the wyeconfiguration, but consume less electric power than consumed whenoperating in the delta configuration. Accordingly, it would bebeneficial to increase the operational flexibility of a wye-deltastarter.

After the electric motor is spinning, electric power may be disconnectedfrom the motor for various reasons, such as a brownout or a lightningstrike. More specifically, switching devices (e.g., contactors) may opento disconnect electric power. Once power is disconnected, the momentumof the rotation may keep the motor spinning, but friction (e.g., airresistance) may begin to slow the motor. As such, the frequency of themotor gradually decreases. Subsequently, the electric motor may berestarted by re-closing the switching devices to connect electric powerto the motor. In some embodiments, such as reliability sensitiveimplementation, it may be desirable to restart the electric motor assoon as possible, for example, while the electric motor is stillspinning. However, since the frequency of the motor is changing, thephase relationship of the motor relative to the electric power source isalso changing, thereby creating a “beat” condition. Therefore, the motormay be out of phase from the source when re-closing the switchingdevices to reconnect electric power to the motor, which may result incurrent oscillations and/or torque oscillations. In some embodiments,minimizing the likelihood and magnitude of current oscillations and/ortorque oscillations may increase the lifespan of the electric motorand/or a connected load. In some embodiments, minimizing peaks in thecurrent may reduces nuisance tripping of protective circuitry (e.g.,circuit breaker or fuses) and, thus, enable the protective circuitry tobe sized more advantageously.

Accordingly, it would be beneficial to minimize the magnitude andlikelihood of current oscillations and/or torque oscillations producedwhen the electric motor is restarted. More specifically, this mayinclude restarting the electric motor when the phase of the electricpower and the electric motor are substantially in phase, when the phaseof the electric power is leading the phase of the electric motor, or atsome other desired condition.

As will be described in more detail below, many of the benefitsdescribed may be enabled by increasing the amount of control over theelectric power supplied to a load. For example, independentlycontrolling each phase of three-phase power may enable detection offaults (e.g., a phase-to-ground short or a phase-to-phase short) whileminimizing the duration, the peak current, and/or the let through energyof the faulty condition. Accordingly, it would be beneficial to utilizea switching device capable of increasing control over electric powersupplied to the load, for example, by enabling each phase of electricpower to be independently controlled.

Additionally, since switching device may be utilized in variousimplementations, such as a wye-delta starter, a reverser, a motor drivebypass, and so forth, it would be beneficial to utilize a switchingdevice that can be modularly configured for various implementations, forexample, to minimize footprint and/or interconnections (e.g., cabling)of the switching devices. More generally, modular arrangements, such assingle-phase switching modules that can be incorporated alone or as agroup, may enable a highly flexible modular design and manufacturingplatform, which allows for assemblies of devices for many differentneeds and markets.

Moreover, while many of the foregoing improvements may be used together,they may also be used separately with significant potential forimprovement in the field of switching and power systems. For example,single-phase switching devices may be used in POW (e.g., timed)application and/or conventional (e.g., non-timed) applications.Additionally, a motor control device (e.g., a wye-delta starter) mayalso be used in POW (e.g., timed) application and/or conventional (e.g.,non-timed) applications. The present disclosure relates to variousdifferent technical improvements in the field, which may be used invarious combinations to provide advances in the art.

DRAWINGS

These and other features, aspects, and advantages of the presentdisclosure will become better understood when the following detaileddescription is read with reference to the accompanying drawings in whichlike characters represent like parts throughout the drawings, wherein:

FIG. 1 is a diagrammatical representation of a set of switching devicesto provide power to an electrical load, in accordance with anembodiment;

FIG. 2 is a similar diagrammatical representation of a set of switchingdevices to provide power to an electrical motor, in accordance with anembodiment;

FIG. 3 is a similar diagrammatical representation of a set of switchingdevices to provide power to an electrical motor, in accordance with anembodiment;

FIGS. 4A-4D is a similar diagrammatical representation of a set ofswitching devices to provide power to a specific application, in thiscase a chiller motor, in accordance with an embodiment;

FIGS. 5A-5C is a diagrammatical representation of three-phase POWswitching to provide power to a load, in accordance with an embodiment;

FIG. 6 is a diagrammatical representation of three-phase POW switchingto disconnect power from a load, in accordance with an embodiment;

FIG. 7 is a perspective view of a single-pole, single current-carryingpath switching device, in accordance with an embodiment;

FIG. 8 is a perspective exploded view of the device of FIG. 7, inaccordance with an embodiment;

FIG. 9 is a top perspective view of certain of the internal componentsand assemblies of the single-pole, single current-carrying pathswitching device, in accordance with an embodiment;

FIG. 10 is a bottom perspective view of the internal components andassemblies of the device, in accordance with an embodiment;

FIG. 11 is a side view of the internal components and assemblies of thedevice, in accordance with an embodiment;

FIG. 12 is a partially sectioned side view of the internal componentsand assemblies of the device in an open position, in accordance with anembodiment;

FIG. 13 is a top perspective view of a movable contact structure for thedevice, in accordance with an embodiment;

FIG. 14 is a partially sectioned side view of the internal componentsand assemblies of the device in an open position, in accordance with anembodiment;

FIG. 15 is a detailed view of one aspect of the device structure, inaccordance with an embodiment;

FIG. 16 is a detailed view of a further aspect of the device structure,in accordance with an embodiment;

FIG. 17A is a detailed view of an optional armature arrangement of thedevice structure, in accordance with an embodiment;

FIG. 17B is a diagrammatical representation of a similar device with adedicated sensing winding or coil, in accordance with an embodiment;

FIG. 18 is a perspective view of a splitter plate for the device, inaccordance with an embodiment;

FIG. 19 is a perspective view of an internal construction of the devicehousing to help channel and cool gases, in accordance with anembodiment;

FIG. 20 is a partially sectional view representing the channeling ofgases during operation of the device, in accordance with an embodiment;

FIG. 21 is a top view of a pair of single-pole switching devices joinedby a mechanical interlock, in accordance with an embodiment;

FIG. 22 is a perspective view of a system assembled with multiplesingle-pole switching devices with electrical interconnects, inaccordance with an embodiment;

FIG. 23 is a perspective view of a mechanical interlock that may be usedin the assemblies, in accordance with an embodiment;

FIG. 24 is an exploded view of the mechanical interlock, in accordancewith an embodiment;

FIG. 25 is a circuit diagram of an operating coil driver circuitry foruse with the single-pole switching device, in accordance with anembodiment;

FIGS. 26A and 26B are a diagrammatical representations of coil currentwaveforms for closing of the device, in accordance with an embodiment;

FIG. 27 is a voltage waveform illustrating timing considerations forclosing the device, in accordance with an embodiment;

FIG. 28 is a block diagram of logic for timing closing of the device, inaccordance with an embodiment;

FIG. 29 is a PWM waveform for determining closing the device, inaccordance with an embodiment;

FIG. 30 is a block diagram of logic for closing the device, inaccordance with an embodiment;

FIG. 31 is a diagrammatical representations of coil control waveformsfor opening of the device, in accordance with an embodiment;

FIG. 32 is a voltage or current waveform illustrating timingconsiderations for opening the device, in accordance with an embodiment;

FIG. 33 is a block diagram of logic for timing opening of the device, inaccordance with an embodiment;

FIGS. 34A and 34B are a PWM waveform for determining opening the device,in accordance with an embodiment;

FIG. 35 is a block diagram of logic for determining opening the device,in accordance with an embodiment;

FIG. 36 is a diagrammatical representation of an alternate embodiment ofan operator coil driving circuit, in accordance with an embodiment;

FIG. 37 is a diagrammatical representation of a power scenario duringswitching of the device, in accordance with an embodiment;

FIG. 38 is a coil operation to temperature relationship, in accordancewith an embodiment;

FIG. 39 is a block diagram of logic for temperature detection (e.g.,relative) and adaptation, in accordance with an embodiment;

FIG. 40 is a similar block diagram of logic for monitoring temperatureduring operation, in accordance with an embodiment;

FIGS. 41A-41D are block diagrams of logic for determining wellness of acomponent, load and/or system based upon monitoring of operator coilparameters, in accordance with an embodiment;

FIGS. 42A-42D is a block diagram of logic for the sequential switchingof single pole switching devices, in accordance with an embodiment;

FIGS. 43A-43H is a set of equivalent circuit diagrams illustrating phasesequential wye-delta switching utilizing single-pole switching devicesfor controlling a three-phase motor, in accordance with an embodiment;

FIG. 44A is a block diagram of logic for the phase sequential wye-deltaswitching, in accordance with an embodiment;

FIG. 44B is plot of current in windings of an electric motor duringphase sequential wye-delta switching, in accordance with an embodiment;

FIGS. 45A-45C is a set of current and voltage waveforms for the phasesequential wye-delta switching, in accordance with an embodiment;

FIG. 46 is a block diagram of logic for switching between wye and deltaconfigurations during operation of a motor, in accordance with anembodiment;

FIGS. 47A-47H is a set of equivalent circuit diagrams illustrating phasesequential wye-delta switching utilizing 6 single-pole switchingdevices, in accordance with certain embodiments;

FIG. 48 is a block diagram of logic for wye-delta motor starting over aseries of starts, in accordance with an embodiment;

FIGS. 49A-49D are circuit diagrams for 8 and 9 pole wye-delta switchingarrangements, in accordance with an embodiment;

FIGS. 50A-50F is a set of equivalent circuit diagrams illustrating phasesequential wye-delta switching referenced to known, predicted, orestimated drive torques applied to a three-phase motor, in accordancewith an embodiment;

FIG. 50G is a plot of torque produced by an electric motor during phasesequential wye-delta switching, in accordance with an embodiment;

FIGS. 51A and 51B is a set of block diagrams of logic for thetorque-referenced and power-referenced phase sequential wye-deltaswitching, in accordance with an embodiment;

FIG. 52 is a voltage or current waveform illustrating timingconsiderations for POW switching based upon an operator-receivedinitiation command, in accordance with an embodiment;

FIG. 53 is a block diagram of logic for operator-initiated POWswitching, such as for starting a polyphase motor, in accordance with anembodiment;

FIG. 54 is a waveform for a motor drive signal and a motor back EMFsignal illustrating timing of the signals during deceleration (oracceleration) of the motor for re-applying drive signals, in accordancewith an embodiment;

FIG. 55 is a block diagram of logic for synchronously reclosing aswitching circuit for re-applying drive signals to a motor, inaccordance with an embodiment;

FIGS. 56A and 56B is a diagrammatical representation of circuitry fordetecting motor conditions utilizing single-pole switching devices and acorresponding timing diagram, respectively, in accordance with anembodiment;

FIG. 57 is a block diagram of logic for detecting motor conditions, inaccordance with an embodiment;

FIGS. 58A and 58B is a diagrammatical representation of alternativecircuitry for detecting motor conditions utilizing multiple single-poleswitching devices and a corresponding timing diagram, respectively, inaccordance with an embodiment;

FIG. 59 is a graphical representation of timing for the motor conditiondetection, in accordance with an embodiment;

FIG. 60 is a diagrammatical representation of a circuit for a 5 polewye-delta starter constructed of multiple single-pole switching devicesinterconnected with one another, in accordance with an embodiment;

FIG. 61 is a top view of an assembly of single-pole switching devices tocreate the circuit of FIG. 60, in accordance with an embodiment;

FIG. 62 is a diagrammatical representation of a circuit for a 6 polewye-delta starter constructed of multiple single-pole switching devicesinterconnected with one another, in accordance with an embodiment;

FIG. 63 is a top view of an assembly of single-pole switching devices tocreate the circuit of FIG. 62, in accordance with an embodiment;

FIG. 64 is a diagrammatical representation of a circuit for an 8 polewye-delta starter constructed of multiple single-pole switching devicesinterconnected with one another, in accordance with an embodiment;

FIG. 65 is a top view of an assembly of single-pole switching devices tocreate the circuit of FIG. 64, in accordance with an embodiment;

FIG. 66 is a diagrammatical representation of a circuit for a 9 polewye-delta starter constructed of multiple single-pole switching devicesinterconnected with one another, in accordance with an embodiment;

FIG. 67 is a top view of an assembly of single-pole switching devices tocreate the circuit of FIG. 66, in accordance with an embodiment;

FIG. 68 is a diagrammatical representation of an circuit for analternative 9 pole wye-delta starter constructed of multiple single-poleswitching devices interconnected with one another, in accordance with anembodiment;

FIG. 69 is a top view of an assembly of single-pole switching devices tocreate the circuit of FIG. 68, in accordance with an embodiment;

FIG. 70 is a diagrammatical representation of a circuit for a 5 polereverser constructed of multiple single-pole switching devicesinterconnected with one another, in accordance with an embodiment;

FIG. 71 is a top view of an assembly of single-pole switching devices tocreate the circuit of FIG. 70, in accordance with an embodiment;

FIG. 72 is a diagrammatical representation of a circuit for a motordrive bypass constructed of multiple single-pole switching devicesinterconnected with one another, in accordance with an embodiment;

FIG. 73 is a top view of an assembly of single-pole switching devices tocreate the circuit of FIG. 72, in accordance with an embodiment;

FIG. 74 is a diagrammatical representation of a three single-poleswitching device configuration used in various control schemes, inaccordance with an embodiment;

FIG. 75 is a diagrammatical representation of a four single-poleswitching device configuration used in various control schemes, inaccordance with an embodiment;

FIG. 76 is a perspective view of two single-pole switching devicesconnected via a bus bar, in accordance with an embodiment;

FIG. 77 is a perspective view of two single-pole switching devices withvarying height power terminals connected via a single connector pin, inaccordance with an embodiment;

FIG. 78 is a perspective view of two single-pole switching devices withmating power terminals connected via a single connector pin, inaccordance with an embodiment;

FIG. 79 is a top view of three single-pole switching devices withvarying height power terminals connected via a single connector pin, inaccordance with an embodiment;

FIG. 80 is a top view of three single-pole switching devices connectedvia a “T” bus bar, in accordance with an embodiment;

FIG. 81 is a block diagram of logic for controlling temperature of anelectric motor, in accordance with an embodiment; and

FIG. 82 is a block diagram of logic for cleaning contactor pads of aswitching device, in accordance with an embodiment.

DETAILED DESCRIPTION

One or more specific embodiments of the present disclosure will bedescribed below. In an effort to provide a concise description of theseembodiments, all features of an actual implementation may not bedescribed in the specification. It should be appreciated that in thedevelopment of any such actual implementation, as in any engineering ordesign project, numerous implementation-specific decisions must be madeto achieve the developers' specific goals, such as compliance withsystem-related and business-related constraints, which may vary from oneimplementation to another. Moreover, it should be appreciated that sucha development effort might be complex and time consuming, but wouldnevertheless be a routine undertaking of design, fabrication, andmanufacture for those of ordinary skill having the benefit of thisdisclosure.

When introducing elements of various embodiments of the presentdisclosure, the articles “a,” “an,” “the,” and “said” are intended tomean that there are one or more of the elements. The terms “comprising,”“including,” and “having” are intended to be inclusive and mean thatthere may be additional elements other than the listed elements.

As described above, switching devices are used in variousimplementations, such as industrial, commercial, material handling,manufacturing, power conversion, and/or power distribution, to connectand/or disconnect electric power from a load. To help illustrate, FIG. 1depicts a system 10 that includes a power source 12, a load 14, andswitchgear 16, which includes one or more switching devices. In thedepicted embodiment, the switchgear 16 may selectively connect and/ordisconnect three-phase electric power output by the power source 12 tothe load 14, which may be an electric motor or any other powered device.In this manner, electrical power flows from the power source 12 to theload 14. For example, switching devices in the switchgear 16 may closeto connect electric power to the load 14. On the other hand, theswitching devices in the switchgear 16 may open to disconnect electricpower from the load 14. In some embodiments, the power source 12 may bean electrical grid.

It should be noted that the three-phase implementation described hereinis not intended to be limiting. More specifically, certain aspects ofthe disclosed techniques may be employed on single-phase circuitryand/or for applications other than power an electric motor.Additionally, it should be noted that in some embodiments, energy mayflow from the source 12 to the load 14. In other embodiments energy mayflow from the load 14 to the source 12 (e.g., a wind turbine or anothergenerator). More specifically, in some embodiments, energy flow from theload 14 to the source 12 may transiently occur, for example, whenoverhauling a motor.

In some embodiments, operation of the switchgear 16 (e.g., opening orclosing of switching devices) may be controlled by control andmonitoring circuitry 18. More specifically, the control and monitoringcircuitry 18 may instruct the switchgear 16 to connect or disconnectelectric power. Accordingly, the control and monitoring circuitry 18 mayinclude one or more processors 19 and memory 20. More specifically, aswill be described in more detail below, the memory 20 may be a tangible,non-transitory, computer-readable medium that stores instructions, whichwhen executed by the one or more processor 18 perform various processesdescribed. It should be noted that non-transitory merely indicates thatthe media is tangible and not a signal. Many different algorithms andcontrol strategies may be stored in the memory and implemented by theprocessor 19, and these will typically depend upon the nature of theload, the anticipated mechanical and electrical behavior of the load,the particular implementation, behavior of the switching devices, and soforth.

Additionally, as depicted, the control and monitoring circuitry 18 maybe remote from the switchgear 16. In other words, the control andmonitoring circuitry 18 may be communicatively coupled to the switchgear16 via a network 21. In some embodiments, the network 21 may utilizevarious communication protocols such as DeviceNet, Profibus, Modbus,Ethernet, to mention only a few. For example, to transmit signalsbetween the control and monitoring circuitry 18 may utilize the network21 to send make and/or break instructions to the switchgear 16. Thenetwork 21 may also communicatively couple the control and monitoringcircuitry 18 to other parts of the system 10, such as other controlcircuitry or a human-machine-interface (not separately depicted).Additionally or alternatively, the control and monitoring circuitry 18may be included in the switchgear 16 or directly coupled to theswitchgear, for example, via a serial cable.

Furthermore, as depicted, the electric power input to the switchgear 16and output from the switchgear 16 may be monitored by sensors 22. Morespecifically, the sensors 22 may monitor (e.g., measure) thecharacteristics (e.g., voltage or current) of the electric power.Accordingly, the sensors 22 may include voltage sensors and currentsensors. These sensors may alternatively be modeled or calculated valuesdetermined based on other measurements (e.g., virtual sensors). Manyother sensors and input devices may be used, depending upon theparameters available and the application. Additionally, thecharacteristics of the electric power measured by the sensors 22 may becommunicated to the control and monitoring circuitry 18 and used as thebasis for algorithmic computation and generation of waveforms (e.g.,voltage waveforms or current waveforms) that depict the electric power.More specifically, the waveforms generated based on input the sensors 22monitoring the electric power input into the switchgear 16 may be usedto define the control of the switching devices, for example, by reducingelectrical arcing when the switching devices open or close. Thewaveforms generated based on the sensors 22 monitoring the electricpower output from the switchgear 16 and supplied to the load 14 may beused in a feedback loop to, for example, monitor conditions of the load14.

As described above, the switchgear 16 may connect and/or disconnectelectric power from various types of loads 14, such as the electricmotor 24 included in the motor system 26 depicted in FIG. 2. Asdepicted, the switchgear 16 may connect and/or disconnect the powersource 12 from the electric motor 24, such as during startup and shutdown. Additionally, as depicted, the switchgear 16 will typicallyinclude or function with protection circuitry 28 and the actualswitching circuitry 30 that makes and breaks connections between thepower source and the motor windings. More specifically, the protectioncircuitry 28 may include fuses and/or circuit breakers, and theswitching circuitry 30 will typically include relays, contactors, and/orsolid state switches (e.g., SCRs, MOSFETs, IGBTs, and/or GTOs), such aswithin specific types of assembled equipment (e.g., motor starters).

More specifically, the switching devices included in the protectioncircuitry 28 may disconnect the power source 12 from the electric motor24 when an overload, a short circuit condition, or any other unwantedcondition is detected. Such control may be based on the un-instructedoperation of the device (e.g., due to heating, detection of excessivecurrent, and/or internal fault), or the control and monitoring circuitry18 may instruct the switching devices (e.g., contactors or relays)included in the switching circuitry 30 to open or close. For example,the switching circuitry 30 may include one (e.g., a three-phasecontactor) or more contactors (e.g., three or more single-pole, singlecurrent-carrying path switching devices).

Accordingly, to start the electric motor 24, the control and monitoringcircuitry 18 may instruct the one or more contactors in the switchingcircuitry 30 to close individually, together, or in a sequential manner.On the other hand, to stop the electric motor 24, the control andmonitoring circuitry 18 may instruct the one or more contactors in theswitching circuitry 30 to open individually, together, or in asequential manner. When the one or more contactors are closed, electricpower from the power source 12 is connected to the electric motor 24 oradjusted and, when the one or more contactors are open, the electricpower is removed from the electric motor 24 or adjusted. Other circuitsin the system may provide controlled waveforms that regulate operationof the motor (e.g., motor drives, automation controllers, etc.), such asbased upon movement of articles or manufacture, pressures, temperatures,and so forth. Such control may be based on varying the frequency ofpower waveforms to produce a controlled speed of the motor.

In some embodiments, the control and monitoring circuitry 18 maydetermine when to open or close the one or more contactors based atleast in part on the characteristics of the electric power (e.g.,voltage, current, or frequency) measured by the sensors 22. Additionallyor alternatively, the control and monitoring circuit 18 may receive aninstruction to open or close the one or more contactors in the switchingcircuitry 30 from another part of the motor system 26, for example, viathe network 21.

In addition to using the switchgear 16 to connect or disconnect electricpower directly from the electric motor 24, the switchgear 16 may connector disconnect electric power from a motor controller/drive 32 includedin a machine or process system 34. More specifically, the system 34includes a machine or process 36 that receives an input 38 and producesan output 40.

To facilitate producing the output 40, the machine or process 36 mayinclude various actuators (e.g., electric motors 24) and sensors 22. Asdepicted, one of the electric motors 24 is controlled by the motorcontroller/drive 32. More specifically, the motor controller/drive 32may control the velocity (e.g., linear and/or rotational), torque,and/or position of the electric motor 24. Accordingly, as used herein,the motor controller/drive 32 may include a motor starter (e.g., awye-delta starter), a soft starter, a motor drive (e.g., a frequencyconverter), a motor controller, or any other desired motor poweringdevice. Additionally, since the switchgear 16 may selectively connect ordisconnect electric power from the motor controller/drive 32, theswitchgear 16 may indirectly connect or disconnect electric power fromthe electric motor 24.

As used herein, the “switchgear/control circuitry” 42 is used togenerally refer to the switchgear 16 and the motor controller/drive 32.As depicted, the switchgear/control circuitry 42 is communicativelycoupled to a controller 44 (e.g., an automation controller. Morespecifically, the controller 44 may be a programmable logic controller(PLC) that locally (or remotely) controls operation of theswitchgear/control circuitry 42. For example, the controller 44 mayinstruct the motor controller/driver 32 regarding a desired velocity ofthe electric motor 24. Additionally, the controller 44 may instruct theswitchgear 16 to connect or disconnect electric power. Accordingly, thecontroller 44 may include one or more processor 45 and memory 46. Morespecifically, the memory 46 may be a tangible non-transitorycomputer-readable medium on which instructions are stored. As will bedescribed in more detail below, the computer-readable instructions maybe configured to perform various processes described when executed bythe one or more processor 45. In some embodiments, the controller 44 mayalso be included within the switchgear/control circuitry 42.

Furthermore, the controller 44 may be coupled to other parts of themachine or process system 34 via the network 21. For example, asdepicted, the controller 44 is coupled to the remote control andmonitoring circuitry 18 via the network 21. More specifically, theautomation controller 44 may receive instructions from the remotecontrol and monitoring circuitry 18 regarding control of theswitchgear/control circuitry 42. Additionally, the controller 44 maysend measurements or diagnostic information, such as the status of theelectric motor 24, to the remote control and monitoring circuitry 18. Inother words, the remote control and monitoring circuitry 18 may enable auser to control and monitor the machine or process 36 from a remotelocation.

Moreover, sensors 22 may be included throughout the machine or processsystem 34. More specifically, as depicted, sensors 22 may monitorelectric power supplied to the switchgear 16, electric power supplied tothe motor controller/drive 32, and electric power supplied to theelectric motor 24. Additionally, as depicted, sensors 22 may be includedto monitor the machine or process 36. For example, in a manufacturingprocess, sensors 22 may be included to measure speeds, torques, flowrates, pressures, the presence of items and components, or any otherparameters relevant to the controlled process or machine.

As described above, the sensors 22 may feedback information gatheredregarding the switchgear/control circuitry 42, the motor 24, and/or themachine or process 36 to the control and monitoring circuitry 18 in afeedback loop. More specifically, the sensors 22 may provide thegathered information to the automation controller 44 and the automationcontroller 44 may relay the information to the remote control andmonitoring circuitry 18. Additionally or alternatively, the sensors 22may provide the gathered information directly to the remote control andmonitoring circuitry 18, for example via the network 21.

To facilitate operation of the machine or process 36, the electric motor24 converts electric power to provide mechanical power. To helpillustrate, an electric motor 24 may provide mechanical power to variousdevices, as described in the non-limiting examples depicted in FIGS.4A-4D. For example, as depicted in FIG. 4A, the electric motor 24 mayprovide mechanical power to a fan 47. More specifically, the mechanicalpower generated by the electric motor 24 may rotate blades of the fan 47to, for example, vent a factory. Accordingly, the switchgear/controlcircuitry 42 may control operation (e.g., velocity) of the fan 47 bycontrolling electric power supplied from the power source 12 to theelectric motor 24. For example, the switchgear/control circuitry 42 maydecrease electric power supplied to the motor 24 to reduce velocity ofthe fan 47. On the other hand, the switchgear/control circuitry 42 mayincrease electric power supplied to the motor 24 to increase velocity ofthe fan 47. As depicted, a sensor 22 may also be included on the fan 47to provide feedback information regarding operation of the fan 22, suchas temperature, velocity, torque, or position, which may be used toadjust operation of the fan 47. In other words, operation of the fan 47may be adjusted in a feedback loop.

Additionally, as depicted in FIG. 4B, the electric motor 24 may providemechanical power to a conveyer belt 48. More specifically, themechanical power generated by the electric motor 24 may rotate theconveyer belt 48 to, for example, move a package along the conveyer belt48. Accordingly, the switchgear/control circuitry 42 may controloperation (e.g., acceleration, velocity, and/or position) of theconveyer belt 48 by controlling electric power supplied from the powersource 12 to the electric motor 24. For example, the switchgear/controlcircuitry 42 may start the conveyer belt 48 by supplying electric powerto the motor 24. On the other hand, the switchgear/control circuitry 42may stop the conveyer belt 48 at a specific position by ceasing electricpower supplied to the motor 24. As depicted, a sensor 22 may also beincluded on the conveyer belt 48 to provide feedback informationregarding operation of the conveyer belt 48, such as temperature,velocity, torque, or position, which may be used to adjust operation ofthe conveyer belt 48. In other words, operation of the conveyer belt 48may be adjusted in a feedback loop.

Furthermore, as depicted in FIG. 4C, the electric motor 24 may providemechanical power to a pump 50. More specifically, the mechanical powergenerated by the electric motor may drive the pump 50 to, for example,move a fluid (e.g., gas or liquid). Accordingly, the switchgear/controlcircuitry 42 may control operation (e.g., pumping rate) of the pump 50by controlling electric power supplied from the power source 12 to theelectric motor 24. For example, the switchgear/control circuitry 42 mayincrease electric power supplied to the motor 24 to increase the pumpingrate of the pump 50. On the other hand, the switchgear/control circuitry42 may decrease electric power supplied to the motor 24 to decrease thepumping rate of the pump 50. As depicted, a sensor 22 may also beincluded on the pump 50 to provide feedback information regardingoperation of the pump 50, such as temperature or pumping rate, which maybe used to adjust operation of the pump 50. In other words, operation ofthe pump 50 may be adjusted in a feedback loop.

As described above, the electric motor 24 may be used to facilitate amachine or process 36. To help illustrate, FIG. 4D depicts a chillersystem 52 that may be used in a process to cool a circulated fluid, suchas in an air conditioning or refrigeration system, which includes achiller 54 and a fluid handler 56. More specifically, the fluid handler56 circulates the fluid (e.g., air or water) into the chiller 54 to coolthe fluid by exchanging heat with a refrigerant in the chiller 54. Tofacilitate cooling the fluid, the chiller 54 includes an evaporator 58,a condenser 60, an expansion device 62, and a compressor 64, which pumpsthe refrigerant (e.g., coolant) in the chiller 54. Accordingly, asdepicted, the compressor 64 includes the electric motor 24 and the pump50.

In operation, the compressor 64 compresses refrigerant gas that iscondensed in the condenser 60. In the condenser 60, heat from therefrigerant gas is exchanged with cooling water or air, which acceptsthe heat required for the condensation phase change. In the expansiondevice 62, the flow of the liquid refrigerant is restricted to reducethe pressure of the refrigerant. In some embodiments, some of therefrigerant may vaporize and absorb heat from surrounding liquidrefrigerant to further lower temperature. In the evaporator 58, thelatent heat of vaporization of the refrigerant absorbs heat from thefluid circulated from the fluid handler 56 to cool the fluid (oftenair).

More specifically, one or more electric motors 24 may drive thecompressor 64 (and/or the pump 50). For example, when the chiller 54 isa centrifugal chiller, the electric motor 24 may rotate an impeller tocompress (e.g., accelerate) refrigerant gas in the chiller 54.Accordingly, the switchgear/control circuitry 42 may control operationof the compressor 64 by controlling electric power supplied to theelectric motor 24 from the power source 12. For example, to increase theflow rate (e.g., compression) of refrigerant gas, the switchgear/controlcircuitry 42 may increase electric power supplied to the electric motor24 to increase torque and/or velocity compressor. In some embodiments,the switchgear/control circuitry 42 may adjust the electric powersupplied by reconfiguring windings of the electric motor 24, forexample, from a wye configuration to a delta configuration.

Mechanical loads driven by motors may have a wide range of physical anddynamic characteristics that may affect the strategies for powering themotors. For example, chiller applications may result in highly inertialloads (e.g., that start slowly and with high torque requirements, andthat stop quickly once power is removed). Other inertial loads may bedifficult to stop and may impose particular torque demands whenstopping. Fans will typically have known torque/speed or power curves,as may certain types of pumps. Given that any desired load may be drivenby the technology described here, corresponding strategies may beimplemented for controlling the application of power.

It should also be noted that, while particular emphasis is placed onpowering electric motors by the present technologies, many other loadsmay benefit from the advances proposed. These may include, but are notlimited to, transformers, capacitor banks, linear and other actuators,various power converters, and so forth.

Basic Point-on-Wave (POW) Switching

As discussed in the above examples, the switchgear/control circuitry 42may control operation of a load 14 (e.g., electric motor 24) bycontrolling electric power supplied to the load 14. For example,switching devices (e.g., contactors) in the switchgear/control circuitry42 may be closed to supply electric power to the load 14 and opened todisconnect electric power from the load 14. However, as discussed above,opening (e.g., breaking) and closing (e.g., making) the switchingdevices may discharge electric power in the form of electric arcing,cause current oscillations to be supplied to the load 14, and/or causethe load 14 to produce torque oscillations.

Accordingly, some embodiments of the present disclosure providetechniques for breaking a switching device in coordination with aspecific point on an electric power waveform. For example, to reducemagnitude and/or likelihood of arcing, the switching device may openbased on a current zero-crossing. As used herein, a “currentzero-crossing” is intended to describe when the current conducted by theswitching device is zero. Accordingly, by breaking exactly at a currentzero-crossing, the likelihood of generating an arc is minimal since theconducted current is zero.

However, closing the switching device is generally non-instantaneous andthe conducted electric power changes rapidly. As such, it may bedifficult to break the switching device exactly on the currentzero-crossing. In other words, even when aiming for the currentzero-crossing it is possible that the switching device actually breaksslightly before or slightly after the current zero-crossing. However,although the current may be relatively low slightly after the currentzero-crossing, the magnitude may be increasing and, thus, cause arcingwith increased magnitude. On the other hand, the magnitude of thecurrent slightly before the current zero-crossing is low and decreasing.As such, the magnitude of any produced arcing may be small and beextinguished when reaching the current zero-crossing. In other words,the switching device may be opened based at least in part on a currentzero-crossing such that the switching device breaks slightly before orat the current zero-crossing.

Similarly, some embodiments of the present disclosure provide techniquesfor breaking a switching device in coordination with a specific point onan electric power waveform. For example, to reduce magnitude of in-rushcurrent and/or current oscillation, the switching device may close basedon a predicted current zero-crossing. As used herein, a “predictedcurrent zero-crossing” is intended to describe where a currentzero-crossing would have occurred assuming the switching device wasclosed and in steady state. In other words, the predicted currentzero-crossing may be a multiple of 180° from a subsequent steady statecurrent zero-crossing. Accordingly, by making exactly at a predictedzero-crossing, the conducted current may increase more gradually,thereby reducing magnitude of in-rush current and/or currentoscillation.

However, when the switching device is open, the current supplied to theswitching device is approximately zero while the voltage isapproximately equal to the source voltage. Since the voltage and thecurrent generally a fixed phase difference in steady-state, the voltagesupplied to the switching device may be used to determine the predictedcurrent zero-crossing. For example, when the voltage leads the currentby 90°, a current zero-crossing occurs 90° after a line-to-line voltagezero-crossing, which may also be 60° after a phase voltagezero-crossing. As used herein, a “line-to-line voltage zero-crossing” isintended to describe when voltage supplied to a switching device is zerorelative to another phase and a “phase voltage zero-crossing” isintended to describe when voltage supplied to the switching device iszero relative to ground. Accordingly, the predicted currentzero-crossing may occur 90° after the line-to-line voltage zero-crossingwhen the voltage is at a maximum.

Since opening the switching device is generally non-instantaneous andthe conducted electric power changes rapidly, it may be difficult tomake the switching device exactly on the predicted currentzero-crossing. In other words, even when aiming for the predictedcurrent zero-crossing it is possible that the switching device actuallymakes slightly before or slightly after the current zero-crossing.However, since the magnitude of the current changes more gradually atthe predicted current zero-crossing, magnitude of in-rush current and/orcurrent oscillation may be reduced. In other words, the switching devicemay be closed based at least in part on a predicted currentzero-crossing such that the switching device makes slightly before,slight after, or at the predicted current zero-crossing.

Although some embodiments describe breaking a switching device based ona current zero-crossing or making the switching device based on apredicted current zero-crossing, it should be understood that theswitching devices may be controlled to open and close at any desiredpoint on the waveform using the disclosed techniques. To facilitateopening and/or closing at a desired point on the waveform, one or moreswitching devices may be independently controlled to selectively connectand disconnect a phase of electric power to the load 14. In someembodiments, the one or more switching devices may be a multi-pole,multi-current carrying path switching device that controls connection ofeach phase with a separate pole. More specifically, the multi-pole,multi-current carrying path switching device may control each phase ofelectric power by movement of a common assembly under the influence of asingle operator (e.g., an electromagnetic operator). Thus, in someembodiments, to facilitate independent control, each pole may beconnected to the common assembly in an offset manner, thereby enablingmovement of the common assembly to affect one or more of the polesdifferently.

In other embodiments, the one or more switching devices may includemultiple single pole switching devices. As used herein a “single poleswitching device” is intended to differentiate from a multi-pole, multicurrent-carrying path switching device in that each phase is controlledby movement of a separate assembly under influence of a separateoperator. In some embodiments, the single pole switching device may be asingle pole, multi-current carrying path switching device (e.g.,multiple current carrying paths controlled by movement of a singleoperator) or a single-pole, single current-carrying path switchingdevice, which will be described in more detail below.

As described above, controlling the making (e.g., closing) of the one ormore switching devices may facilitate reducing magnitude of in-rushcurrent and/or current oscillations, which may strain the load 14, thepower source 12, and/or other connected components. As such, the one ormore switching devices may be controlled such that they make based atleast in part on a predicted current zero-crossing (e.g., within a rangeslightly before to slightly after the predicted current zero crossing).

To help illustrate, closing the switching devices to provide three-phaseelectric power to an electric motor 24 in a wye configuration isdescribed in FIGS. 5A-5C. More specifically, FIG. 5A illustrates thevoltage of three-phase electric power (e.g., a first phase voltage curve66, a second phase voltage curve 68, and a third phase voltage curve 70)provided by a power source 12. FIG. 5B illustrates the line to neutralvoltage supplied to each terminal (e.g., first terminal voltage curve72, second terminal voltage curve 74, and third terminal voltage curve76) of the electric motor 24. FIG. 5C illustrates line current suppliedto each winding (e.g., first winding current curve 77, second windingcurrent curve 78, and third winding current curve 80) of the electricmotor 24. As described above, the waveforms depicted in FIGS. 5A-5C maybe determined by control and monitoring circuitry 18 based onmeasurements collected by the sensors 22.

As depicted, between t0 and t1, electric power is not connected to theelectric motor 24. In other words, each of the switching devices isopen. At t1, one or more switching devices are closed to start currentflow from the power source 12 in two phases (e.g., a first phase and asecond phase) of the electric motor 24. To minimize inrush currentand/or current oscillations, a first phase and a second phase areconnected based upon a predicted current zero-crossing. Accordingly, asdepicted in FIG. 5A, the first phase and the second phase are connectedwhen the line-to-line voltage of the first phase (e.g., first phasevoltage curve 66) and the second phase (e.g., a second phase voltagecurve 68) is at a maximum (e.g., 90° after a line-to-line voltagezero-crossing). Once connected, the first phase of the electric powerflows into the first winding of the electric motor 24, the second phaseof the electrical flows into the second winding of the electric motor24, and the third winding of the electric motor 24 is at an internalneutral (e.g., different from line neutral), as depicted in FIG. 5B.Additionally, since the two phases are connected at a predicted currentzero-crossing, the current supplied to the first winding (e.g., firstwinding current curve 77) and the second winding (e.g., second windingcurrent curve 78) start at zero and gradually increase, as depicted inFIG. 5C, thereby reducing magnitude of in-rush current and/or currentoscillations supplied to the first and second windings.

After the first two phases are connected, at t2, the one or moreswitching devices are closed to connect a third phase of the electricpower to the electric motor 24. Similar to the first phase and thesecond phase, to minimize inrush current and/or current oscillations,the third phase is also connected based upon a predicted currentzero-crossing. Accordingly, as depicted in FIG. 5A, the third phase isconnected when sum of line-to-line voltage between the first phase(e.g., first phase voltage curve 66) and the third phase (e.g., thirdphase voltage curve 70) and the line-to-line voltage between the secondphase (e.g., second phase voltage curve 68) and the third phase (e.g.,third phase voltage curve 70) is at a maximum (e.g., a predicted currentzero-crossing), which occurs when the line-to-line voltage between thefirst phase and the second phase is at a minimum and third phase is at amaximum.

It should be noted that although the third phase is depicted as beingconnected at the first such subsequent occurrence, the third phase mayadditionally or alternatively be connected at any subsequent occurrence,for example at t3. Once connected, the third phase of the electric powerflows into the third winding of the electric motor 24, as depicted inFIG. 5B. Additionally, since the third phase is connected based upon apredicted current zero-crossing, the third winding current 80 graduallychanges from zero, as depicted in FIG. 5C, thereby reducing magnitude ofin-rush current and/or current oscillations supplied to the thirdwinding.

Additionally, as described above, controlling the breaking (e.g.,opening) of the one or more switching devices may facilitate reducinglikelihood and/or magnitude of arcing, which may strain and/or wearcontactor pads in the switching devices and/or other connectedcomponents. As such, the one or more switching devices may be controlledsuch that they break based at least in part on a current-zero crossing(e.g., within a range slightly before to at the current zero-crossingacross that switching device).

To help illustrate, opening the switching devices to disconnectthree-phase electric power from an electric motor 24 is described inFIG. 6. More specifically, FIG. 6 depicts the current supplied to thewindings (e.g., first winding current curve 77, second winding currentcurve 78, and third winding current curve 80) of the electric motor 24.As described above, the waveform depicted in FIG. 6 may be determined bycontrol and monitoring circuitry 18 based on measurements collected bythe sensors 22.

As depicted, prior to t4, electric power is connected to the electricmotor 24. In other words, each of the switching devices is closed. Att5, one or more of the switching devices is opened to disconnect thethird phase of the electric power from the electric motor 24. Asdescribed above, to minimize arcing, the third phase disconnected isbased at least in part on a current zero-crossing in the third phase ofelectric power. Accordingly, as depicted, the third phase isdisconnected when the current supplied to the third winding (e.g., thirdwinding current curve 80) is approximately zero. Once disconnected, thecurrent supplied to the second winding current the first winding currentadjust to the removal of the third phase.

After the third phase is disconnected, the one or more of the switchingdevices are opened to disconnect the other two phases (e.g., the firstphase and the second phase) of electric power to the electric motor 24at t6. Similar to disconnecting the third phase, to minimize arcing, thefirst phase is disconnected based at least in part on a currentzero-crossing in the first phase of electric power and the second phaseis disconnected based at least in part on a current zero-crossing in thesecond phase of electric power. Accordingly, as depicted, the firstphase and the second phase are disconnected when current supplied to thesecond winding (e.g., second winding current curve 78) and the firstwinding (e.g., first winding current curve 77) are approximately zero.Once disconnected, the electric power supplied to the electric motor 24begins to decrease. It should be noted that although the first phase andthe second phase are depicted as being disconnected at the firstsubsequent current zero-crossing, the first and second phase mayadditionally or alternatively be disconnected at any subsequent currentzero-crossings.

Single-pole, Single Current-carrying Path Switching Device

FIGS. 7-24 depict a presently contemplated arrangement for providing asingle-pole, single current-carrying path switching device. The devicemay be used in single-phase applications, or very usefully in multiphase (e.g., three-phase) circuits. It may be used alone or to formmodular devices and assemblies such as for specific purposes asdescribed below. Moreover, it may be designed for use in POW powerapplication, and in such applications, synergies may be realized thatallow for very compact and efficient designs due, as least in part, tothe reduced operator demands, reduced arcing, and improvedelectromagnetic effects during the application of current through thedevice.

It should be noted that various embodiments of the single-pole switchingdevices may be used in single current-carrying path applications andalso in multi current-carrying path applications. That is, references tosingle-pole switching devices throughout the disclosure may refer tosingle-pole, single current carrying path switching devices,single-pole, multiple current carrying path switching devices, or somecombination thereof. In some embodiments, a single-pole, multiplecurrent-carrying path switching device may allow for the repurposing ofcertain devices as modular three-phase circuits. For example, asingle-pole, multiple current-carrying path may refer to a switchingdevice with three current-carrying paths that have been interconnectedto provide a single phase of power. Additionally, in some embodiments,three single-pole, single current-carrying path switching devices mayeach be configured to provide a separate phase of power (e.g.,three-phase) and can be independently and/or simultaneously controlledin various beneficial configurations, as described in detail below. Itshould be understood, that the single-pole switching devices may bemodularly configured to provide any number of power phases.

FIG. 7 illustrates a switching device 82 designed for use in certain ofthe applications described in the present disclosure. In the embodimentillustrated, a switching device is a single-pole, singlecurrent-carrying path device in the form of a contactor 84. Thecontactor 84 generally includes an operator section 86 and a contactsection 88. As described more fully below, the operator section includescomponents that enable energization and de-energization of the contactorto complete and interrupt a single current-carrying path through thedevice. The section 88 includes components that are stationary and othercomponents that are moved by energization and de-energization of theoperator section to complete and interrupt the single-carrying path. Inthe illustrated embodiment, the upper conductive section has an upperhousing 90, while the operator section has a lower housing 92. Thehousings fit together to form a single unitary housing body. In theillustrated embodiment flanges 94 extend from the lower housing allowingthe device to be mounted in operation. Other mounting arrangements maycertainly be envisaged. A line-side conductor 96 extends from the deviceto enable connection to a source of power. A corresponding load-sideconductor 98 extends from an opposite side to enable the device to becoupled to a load. In other embodiments, conductors may exit the housing90 and 92 in other manners. In this illustrated embodiment the devicealso includes an upper or top-side auxiliary actuator 100 and a sidemount auxiliary actuator 102.

FIG. 8 illustrates certain of the mechanical, electrical and operationalcomponents of the contactor in an exploded view. As shown, the operatorsection is mounted in the lower housing 92 and includes an operatordesignated generally by reference numeral 104 which itself is acollection of components including a magnetic core comprised of a yoke106 and a central core section 108. A return spring 110 is mountedthrough the central core section 108 as described more fully below forbiasing movable contacts towards an open position. An operator coil 112is mounted around the core section 108 and between upturned portions ofthe yoke 106. As will be appreciated by those skilled in the art, thecoil 112 will typically be mounted on a bobbin and is formed of multipleturns of magnet wire, such as copper. The operator includes leads 114,which in this embodiment extend upwardly to enable connection to theoperator when the components are assembled in the device. As will alsobe appreciated by those skilled in the art, the core, including the yokeand central core section, along with the coil 112 form an electromagnetwhich, when energized, attracts one or more parts of the movable contactassembly described below, to shift the device between an open positionand a closed position.

A movable contact assembly 116 similarly includes a number of componentsassembled as a sub-assembly over the operator. In the embodimentillustrated in FIG. 8, the movable assembly includes an armature 118that is made of a metal or material that can be attracted by fluxgenerated by energization of the operator. The armature is attached to acarrier 120 which typically is made of a non-conductive material, suchas plastic or fiberglass, or any other suitable electrically insulatingmaterial. A conductor assembly 122 is mounted in the carrier and ismoved upwardly and downwardly by movement of the carrier under theinfluence of electromagnetic flux that draws the armature downwardly,and, when the fluxes are removed, the entire assembly may be movedupwardly under the influence of the return spring 110 mentioned above.

The device further includes a stationary contact assembly 124. In theillustrated embodiment, this contact assembly is formed of multiplehardware components, including a mounting assembly 126 that is fittedbetween the lower housing 92 and the upper housing 90. This mountingassembly will typically be made of an electrically non-conductivematerial, and it includes various features for allowing the mounting ofthe line and load-side conductors 96 and 98. It may be noted that thestructure illustrated in FIG. 8 has been rotated 180 degrees as comparedto that of FIG. 7. Each conductor includes a contact pad that comes intocontact with a corresponding contact pad of the movable contact assemblywhen the device is closed or “made”. Moreover, turnbacks 128 areprovided on each conductor and may be screwed or riveted into place, orattached by any other suitable method, and at least partially span thecontact pad of the corresponding conductor. In the final assembly, theseturnbacks are fitted adjacent to a series of splitter plates or shunts130 on either side. As described more fully below, when the device makesor breaks, any arcing that occurs can be driven to the turnbacks andsplitter plates where the arc is divided into several smaller arcs andionized particles and hot gasses are cooled and routed toward theexterior device.

FIGS. 9 and 10 illustrate the same device assembled in top and bottomperspective views, with certain of the components removed, includingcertain housing sections to illustrate the interior components and theirinterior connection. In particular, as shown in FIG. 9, the coil 112 ofthe operator is positioned in a lower location, although in practice thedevice may be mounted in various orientations. The mounting assembly 126holding the line and load-side conductors is fitted above the operatorcoil and the movable contact assembly 116 is position above the mountingassembly such that contact pads of movable contacts within this assemblyare positioned in facing relation to corresponding contact pads on theconductors. More detail regarding the various components of theseassemblies is provided below. As can also be seen in FIGS. 9 and 10,guides 132 may be formed, such as in the mounting assembly 126 forreceiving the terminals of the operator coil. In this illustratedembodiment the terminals extend upwardly and are formed so that plug-inconnections can be made to the operator coil. As will be appreciated bythose skilled in the art, in operation, a signal that energizes theoperator coil is provided by way of the terminals, and typical signalsmay include alternating current (A/C) or direct current (DC) signals,such as 24 or 48 vDC signals. Although AC signals may be provided forthe operator coil, in some applications, such as POW energizationstrategies, predictability in times of closure and opening are providedby DC signals. In some alternative embodiments the terminals, or leadsfor the operator coil may be caused to exit other locations in device,such as through the lower housing. Such applications may provide forplug-in mounting of the contactor or any similar switching device suchthat contacts are made for at least the operator by simply mounting thedevice on a suitable base. In some arrangements it may also be suitableto allow for power, both line and load, to be made through such a base.

FIGS. 11 and 12 provide additional detail of the currently contemplatedsingle-pole, single current-carrying path switching device. As shown inFIG. 11, the operator coil 112 is disposed within the yoke 106 such thatthe yoke channels flux generated by operator coil when energized. Inthis arrangement, the return spring 110 is provided around an alignmentpin 134 that is fixed to and moves with the movable contact assembly,and specifically in this arrangement is mounted to the carrier. FIG. 11illustrates the foregoing components in a de-energized or open positionof the device. In this position, the movable contact assembly isdistanced from the stationary contacts of the conductors so thatcurrent-carrying path through the device is interrupted. The device isthus electrically open.

FIG. 12 illustrates the same components, in a view in which certain ofthem have been shown in section to illustrate their inter-relationshipand operation. Here again, the device is shown in an electrically openposition that will exist when the operator is de-energized prior tomaking or after breaking. As shown in FIG. 12, in the de-energizedposition, the entire movable contact assembly is held in a raisedposition by the return spring 110. Here again, the device may beoriented differently so that the terms “raised” or “lowered” or similarterms are intended as only given the orientation shown in the figures.In this position, the armature 118 is separated from the operatorassembly, in particularly from the yoke 108 and the core 108. Thecarrier 120 holds the conductor assembly 122 spaced from the contactpads of the line and load-side conductors 96 and 98. The assembly isillustrated as including guides 132 (see FIGS. 9 and 10) through edgethe terminals 114 may be routed.

In the currently contemplated embodiment, to reduce size and weight butto provide an excellent working structure, a guide or alignment pin 134is provided in the movable assembly. The pin may be secured in place byany suitable means, such as a clip or retaining ring in the carrier. Thepin is recessed within the carrier to provide the desired degree ofperpendicularly and alignment with the other components of the movablestructure. The operator assembly, on the other hand, comprises one ormore core windings 136 which are made of a series of electricallyinsulated conductive wire, such as copper. The wires typically wound ona bobbin 138 which is placed between the yoke 106 and the core section108. The core assembly is typically formed as a separate component whichis assembled with the other elements of the other elements of theoperator during manufacture. In the illustrated embodiment, the coresection 108 is formed as a cylindrical structure having a centralaperture 140 for receiving the alignment pin 134. An extension 142 ofthis core section is affixed to a lower opening in the yoke 106, such asby staking, threading, or any suitable means. The aperture 140 comprisesat least two sections, including a central alignment section 144 that isdimensioned to fit relatively snuggly with the alignment pin, but toallow for easy movement of the alignment pin therein, providing thedesired alignment function. An upper recess 146 is somewhat enlarged informs of shoulder within the core section to receive the return sprig110 and to form a foundation against which the return spring bearsduring operation. In the depicted embodiment, the return spring 110 isprovided in a convenient location, but may be provided in otherlocations in other embodiments.

The upper portion of the carrier 120 includes a window 150 in which theconductor assembly 122 is positioned. The window is contoured to receiveand to hold in place a movable conductor biasing spring 152 that enablessome movement of the conductor assembly 122 as it comes into contactwith the line and load-side conductors 196 and 198. As will beappreciated by those skilled in the art, in the illustrated embodiment,the conductor assembly 122 includes a turnback element, a conductivebridge or spanner, and contact pads affixed to this spanner. The spannerwill typically be made of a highly conductive material, such as copper,and the contact pads will be made of a conductive material that isnevertheless resistant to arcing that may occur, such as silver,silver/tin oxide, silver nickel alloys, and so forth.

The line and load-side conductors 96 and 98 may be mounted to themounting assembly 126 in any suitable manner, such as by screws orrivets 154. As can be best seen in the exploded view of FIG. 8, contactpads of the line and load-side conductors are positioned to come intocontact with the contact pads of the movable conductor assembly when thedevice is closed or “made”. The turnbacks 128 fit around this contactpad and are themselves are secured by fasteners. One or more insulativeelements, such as synthetic membranes may be placed between theturnbacks 128 and the conductors 96 and 98 when desired. In theillustrated embodiment bumps 156 are formed on the turnbacks to promotemigration of any arcs that are formed during operation of the device.

The elements of the movable contact assembly are illustrated in greaterdetail in FIG. 13. Here again, the conductor assembly 122 may include anupper auxiliary actuator 100, where desired. A side auxiliary actuator102 may also be included. The assembly itself is formed around theconductor 158 which forms the bridge for the structure. Contact pads 160are affixed to a lower side of this conductor and come into contact withthe stationary contact pads of the line and low-side conductors when thedevice is closed or energized. The carrier assembly 122 itself alsoincludes a base 164 to which the armature 118 is secured by appropriatefasteners 166. Again, the alignment pin 134 extends downwardly from thebase 164 of the carrier.

Additionally, a turnback 162 is formed in a metallic element that restsadjacent to the conductive span 158. In the illustrated embodiment theturnback 162 also contacts the conductor biasing spring 152 to hold themovable conductors in a lower position in the window 150. In someembodiments, the turnback 162 may shape the magnetic field duringopening by providing an alternate path for the current. Morespecifically, the arc may be attached up onto a face 163 of the turnback162 and stay there during the arcing event. In this manner, the arcingexperienced by the contactor pads 160 may be reduced, thereby enablingthe ionized atmosphere around the contact pads 160 to regain theirdielectric strength

FIG. 14 illustrates the foregoing structure in the energized or shiftedposition. This position corresponds to energization of the operatorcoil, typically by application of a DC voltage. So long as the coil isenergized, the coil generates a flux that is channeled by the yoke 106and core 108 of the operator assembly, drawing the armature toward theoperator assembly, shifting the entire movable contact assemblydownwardly. Thus, in FIG. 14 the armature 118 is illustrated in adownward position adjacent to the yoke 106. The alignment pin has guidedthe movable assembly in its motion, and protrudes further into thealignment portion 144 of the aperture in the core section 108. Thereturn spring is shown compressed. The movable contacts, hidden herebehind the fasteners of the turnbacks in the stationary contact assemblyare in contact to complete a current carrying path through the device.In the presently contemplated embodiment, a single current carrying pathis defined through the device that includes the line-side conductor 96,the load-side conductor 98, the contact pads of these conductors, themovable contact pads of the movable contact assembly, and the conductivespanner of the movable contact assembly. The device is thus asingle-pole device that is suitable for passing current of a singlephase of AC power (or DC power).

Certain presently contemplated details of this assembly are illustratedin FIGS. 15 and 16. As shown in FIG. 15, to promote saturation of theyoke 106, upper ends of the yoke may have a reduced dimension 170 in aregion where they come into contact with or are close to the armature118 when shifted. Such saturation may facilitate holding of the movableassembly in the shifted position while reducing required holding currentin the coil. As shown in FIG. 16, moreover, a gap 172 may be formedbetween the upper surface of the central core section 108 of theoperator assembly and the armature 118. Such gaps may be formed by airspacing, insulating elements, or by any similar means. Such gaps may aidin avoiding residual flux in the armature 118, yoke 106 and/or core 108that may otherwise preclude or slow the separation or movement of themovable assembly upon de-energization of the operator coil.

FIG. 17A illustrates a presently contemplated alternative configurationin which current may be sensed by the effects of the current on signalsthrough the operator coil itself. That is, before the device is shiftedor energized to make or close the device, no current should flow betweenthe line and low-side conductors. Once the device is shifted, however,current may flow through the single current-carrying path as describedherein. When current does flow, various mechanisms may be envisaged forsensing the current, including separate current sensors, which may beinternal or external to the switching device. It is presentlycontemplated, however, that certain elements of the structure maythemselves permit sensing of the main current through the singlecurrent-carrying path. Such sensing may, for example, be performed bymonitoring current through the operator coil described below. Thecurrent to the operator coil may be perturbed in detectable ways bycurrent through the single current-carrying path. Such perturbations maybe evaluated by the coil control circuitry and used as an indication ofthe main current through the device. In the illustration of FIG. 17A,the armature 118 may provide sufficient coupling of flux generated bythe main current through the device with current through the operatorcoil to enable such sensing. Where enhanced sensing is desired, it ispossible to design the armature 118 to promote the sensing, such as bythe inclusion of wings 168 or other structures that tend to enhance theuptake of flux through the armature that may be generated by the currentthrough the main current-carrying path.

An alternative or complimentary arrangement for sensing current isillustrated in FIG. 17B. In this arrangement, one or more sense windings174 are provided on the operator coil 112. The sense winding may be madeof a similar or different material, and will typically not require morethan one or a few turns. Where desired, a secondary groove may beprovided in the bobbin discussed above to receive the sense winding. Thesense winding, where provided, will have lead as illustrated in FIG. 17Bthat will be coupled to measurement circuitry used to detect currentthrough the main current-carrying path of the device.

The contactor illustrated in the figures also includes integralstructures for routing plasma and hot gasses and facilitating theirmigration out of the device where desired. As illustrated in FIGS. 18and 19, these might include features of the splitter plates 130 and theupper housing. As shown in FIG. 18, for example, a current design forthe splitter plates 130 includes stake ridges that allow the plates tobe pressed into place within the upper housing and held into place,preventing their withdrawal. A lower recess 178 is formed in each plate,and upper recesses 180 are formed that enable the passage of plasma andhot gasses during opening and closing of the device. As best illustratedin FIG. 19, the upper housing may include alignment features, such asrecesses 180 that may also enable the passage of operator coil leads,where such designs are used. Within the upper housing, plate guides 182may be formed that receive the splitter plates therebetween, and holdthe splitter plates in spaced relation with one another. On ends of theinterior surface of the upper housing, gas guides 184 may be formed thatare separated from one another by grooves 186. These may be placed ingeneral alignment with the recesses 180 formed in the splitter plates.Gasses may thus be channeled upwardly around the movable contactassembly, through the upper recesses 180, which form passage ways withthe upper interior wall of the upper housing, and then downwardlythrough the grooves 186. The gasses may exit gaps formed between lineand load-side conductors and the upper housing. In the illustratedembodiment, the upper housing (and where desired the lower housing andeven the mounting assembly for the stationary contact assembly) may bebilaterally symmetrical so that its orientation is arbitrary, greatlyfacilitating assembly of the device. Such innovations may alsofacilitate ease of manufacturing and reduced number of different parts.

FIG. 20 illustrates a cross-sectional view of the singlecurrent-carrying path switching device. More specifically, when theswitching device is closed (e.g., core windings 136 are energize), asindicated by arrow 188 in FIG. 20, a single current-carrying path isestablished through the device when closed, allowing for single-poleoperation. As discussed in greater detail below, the device may be mademuch smaller physically than previous devices of the same type. This isparticularly true owing to the mechanical design of the components. Thedesign around a single-pole strategy rather than a three-phase strategy,and so forth. The device may be particular reduced in size and mass bythe use of POW switching strategies which greatly reduce arcing and wearwithin the device. As also noted elsewhere in the present discussion,where the switching devices used for three-phase applications, and POWswitching strategies are employed, adjusting order and/or timing ofopening/closing switching devices may greatly prolong the life of thedevice while allowing for reduced size and mass. The reduction in sizeand mass affectively also reduces the cost of the individual components,particularly the relatively expensive conductive materials used.Further, smaller devices may also reduce the electrical enclosure usedto house these components and, thus, reduce the amount of space within afactory or facility occupied by such components.

On the other hand, when the switching device opens from the closedposition plasma and/or gasses may be generated. Accordingly, asindicated by arrow 190, the plasma and/or gasses are routed upwardlythrough passageways and the splitter plates 130 and then downwardlythrough grooves in the upper housing 90. In fact, such routingfacilitates interruption of current through the device by the action ofthe splitter plates 130, and also significantly cools plasma and gassesas they are routed through the device and exit.

The single-pole, single current-carrying path device described above maybe used in a variety of applications and ways. For example, the devicemay be energized by controlled DC currents as described elsewhere in thepresent disclosure. Such control facilitate carefully timed switching,such as for POW switching strategies. The device may be used forsingle-phase switching or multi-phase switching, such as in three-phasesystems. The reduced size, weight and mass of the device discussed abovegreatly facilitate the assembly of the device in various ways, promotinga modular approach to a system design. As discussed below, suchmodularity may enable the construction of a wide range of complexdevices that have heretofore been designed with three-phase contactors,relays and other switches, complex wiring, complex assembly, and soforth.

One mechanism for enabling the interconnection of the devices may bebased around the use of mechanical interlocks that are positionedbetween mated devices. FIGS. 21-24 illustrate the use such interlocks.In the illustration of FIG. 21, two switching devices 82 and 82′ areshown positioned side-by-side with an assembly 192. The assemblyincludes an interlock 194 that is positioned between, secured to andthat interfaces with the side auxiliary actuators of the devices asdescribed above. As shown in FIG. 22, various assemblies of this typemay be envisaged. In the more complex assembly of FIG. 22, a number ofswitching devices are positioned side-by-side, with interlocks 194 beingplaced between certain devices that should not be switched or energizedat the same time. Owing to the particular construction and design of thedevices it has been found that reduced distances may be allowed whilenevertheless respecting requirements of electrical codes. Where desired,to define the desired circuitry, one or more conjunctive jumpers 196 maybe routed between line and/or load-side conductors as generally shown inFIG. 22. Where desired, insulated materials may be placed between suchjumpers to enable definition of complex circuitry that includes thecurrent-carrying paths defined by the modular devices. Pairs 198 of thedevices may be positioned side-by-side, while other pairs are positionedside-by-side with the interlocks 194 provided therebetween.

Again, the interlocks may enable mechanical control of the modularswitching devices, and in particular prevent two switching devices frombeing closed at the same time. As will be appreciated by those skilledin the art, many power circuits require that such mutual energizationmay be avoided, and the interlocks enable a simple mechanism to maintainthe current-carrying path open through one device while it is closedthrough one another. A currently contemplated design for the interlockas illustrated in FIGS. 23 and 24. The interlock may include a housing200 that is generally symmetrical about a vertical center line allowingfor reduction in parts because only a front and a back of the housingare required. The housing may be structured to be easily mounted betweenadjacent module switching devices. The housing may include a windowopening 202 on both sides through which an actuating element 204 isaccessible. The element 204 interfaces mechanically with the sideauxiliary actuators of the switching devices described above (see, e.g.,FIG. 7). As best illustrated in FIG. 24. A current design for theinterlock includes self-similar lever arms 206 and 208 that are mountedpivotally within the housing. Pivot pins 210 and 212 enable pivotalmovement of the lever arms 206 and 208. These may be integrally formedwith the housing, or may be defined by separate components (e.g., rollpins) inserted in the housing. Each lever arm carries a respectiveactuating element 204, with one element extending on one side of thestructure and the other element extending on an opposite side. Eachlever arm includes an integral cam arrangement 214 and 216 that contactone another to prevent one of the lever arms from moving to a downwardposition when the other lever arm is already in a downward position.Thus, when connected to the side auxiliary actuators of two modularswitching devices that are mounted side-by-side, only one of theactuating elements 204 is allowed to a lower position at a time. Whenthe energized and shifted switching device is de-energized and shiftedto an open position then, interference between the integral cams iseliminated and one or the other device is then free to shift to itsenergized or closed position. Many advantages may flow from theinterlock arrangement illustrated, particularly the simplicity of thestructure, the reduction in the number of parts, the ability tofabricate the parts from easily-molded materials (typicallynon-conductive plastics) and the ease of manufacture. In the illustratedembodiment, as noted above, the housing may comprise two self-similarhousing shelves, while the lever arms 206 and 208 may also be identical,as may the actuating elements 204.

Operation of a Single-pole Switching Device

Referring to FIG. 25, based on the above described switching device(e.g., single-pole, single current-carrying path switching device),designated in this figure by reference numeral 218, operation (e.g.,opening and closing) of the switching device 218 is based on controllingelectric power supplied to the operating coil 220. To control operationof the single-pole, single current-carrying path switching device 218,as well as any other switching device with an operating coil, anoperating coil driver circuitry 222 may be utilized. To simplifydiscussion, the operating coil driver circuitry 222 will be described inrelation to the single-pole, single current-carrying path switchingdevice 218 described above. As depicted, the operating coil drivercircuitry 222 includes a processor 224, memory 226, an SR flip-flop 228,a comparator 230, a switch 232, and a flyback diode 234. Morespecifically, as will be described in more detail below, the memory 226may be a tangible non-transitory medium that stores computer-readableinstructions that when executed perform various processes described.Accordingly, in some embodiments, the processor 224 and memory 226 maybe included in the automation controller 44 or control and monitoringcircuitry 18. It should be noted that although the SR flip-flop 228 andthe comparator 230 are described as discrete hardware components, inother embodiments, they may be implemented by the processor 224 ascomputer readable instructions.

As will be described in more detail below, the operating coil drivercircuitry 222 controls operation of the switching device 218 bycontrolling the current in the operating coil (i.e., Icoil). In thedepicted embodiment, the operating coil current may be determined bymeasuring the voltage at node 236 (i.e., Vnode). More specifically,since the operating coil current flows through resistor 238 to ground,the operating coil current is equal to the voltage at node 236 dividedby the resistance of the resistor 238. As such, the resistor 238 isgenerally referred to as a current measuring resistor. In other words,the voltage at node 236 may be used as a proxy for the operating coilcurrent.

Additionally, as depicted, the node voltage is applied to thenon-inverting terminal of the comparator 230 and compared to a referencevoltage (i.e., Vref), which is applied to the inverting terminal of thecomparator 230. More specifically, the processor 224 outputs a voltagethat is smoothed into the DC reference voltage by resistor 240 andcapacitor 242, which corresponds with the voltage expected to bemeasured at node 236 when the target (e.g., desired) operating coilcurrent flows through resistor 238. In other embodiments, the processor224 may include a digital-to-analog (DAC), thereby obviating theresistor 240 and the capacitor 242. In this manner, the referencevoltage may be equal to the target operating coil current multiplied bythe resistance of resistor 238.

Accordingly, when the node voltage is higher than the reference voltage,the output of the comparator 230 is high indicating that the operatingcoil current is higher than the target. On the other hand, when the nodevoltage is lower than the reference voltage, the output of thecomparator 230 is low indicating that the operating coil current islower than the target. In other words, the processor 224 may indicatethe target operating coil current with the reference voltage.

The result of the comparison performed by the comparator 230 is appliedto the R terminal of the SR flip-flop 228. At the S terminal of the SRflip-flop 228, the processor applies a trigger signal 244, whichperiodically goes high to set the SR flip-flop 228. Based on the resultof the voltage comparison and the trigger signal 244, the SR flip-flop228 outputs a pulse-width-modulated (PWM) signal to the switch 232 andthe processor 224. More specifically, the PWM signal is low when theinput from the comparator 230 is high, thereby instructing the switch toturn off and disconnect electric power from the operating coil 220. Onthe other hand, the PWM signal goes high when the input from comparator230 is low and the trigger signal 244 is high, thereby instructing theswitch 232 to turn on and supply electric power from the power supply246 to the operating coil 220.

In this manner, the trigger signal 244 is input to the SR flip-flop 228to facilitate generating the PWM signal by periodically attempting toturn on the switch 232. In some embodiments the frequency of the triggersignal 244 may be based at least in part on desired resolution, howquickly current decays in the coil 220, and/or line frequency of thepower supply 246. For example, when the line frequency is 60 Hz, thetrigger signal may have a frequency of 21.6 kHz (i.e., 1/(60*360)) toachieve a one electrical degree resolution.

Based on the PWM signal, the switch 232 selectively connects ordisconnects the operating coil 220 from electric power supplied by thepower supply 246 to a DC bus 248. More specifically, the power supply246 may output DC electric power to the DC bus 248 based on an externalAC or DC power source, such as power source 12. In some embodiments, thepower supply 246 may store some electric power to decouple the operatingcoil control circuitry 222 from the power source. For example,decoupling may reduce the effect of variations in the power source, suchas a brown out, on the operation of the operating coil control circuitry222.

As described above, when the PWM signal is high, the switch 232 connectsthe operating coil 220 to the DC bus 248 to supply electric power to theoperating coil 220. On the other hand, when the PWM signal is low, theswitch 232 disconnects the operating coil 220 from the DC bus 248 toremove electric power from the operating coil 220. In this manner, thePWM signal may control the duration the electric power is connected and,thus, the operating coil voltage.

More specifically, the operating coil voltage may be equal to the DC busvoltage when the switch 232 is on and equal to voltage across theflyback diode 234 when the switch 232 is off. As such, the averageoperating coil voltage (i.e., voltage drop across the operating coil220) may approximately equal to the DC bus voltage times the PWM signalduty cycle. Since the operating coil current is directly related to theoperating coil voltage, the operating coil current may also becontrolled by adjusting the duty cycle of the PWM signal. For example,when duty cycle is increased, the operating coil current increases and,when the duty cycle is decreased, the operating coil current decreases.

Accordingly, aside from providing the reference voltage and the triggersignal 244, the operating coil current may be adjusted to the targetcoil current relatively independent from the processor 224. For example,when the operating coil current is lower than the target, the SRflip-flop 228 outputs the PWM signal to instruct the switch 232 toconnect electric power from the power supply 34 to the operating coil220. On the other hand, when the comparator 230 determines that theoperating coil current is higher than the target, the SR flip-flop 228outputs the PWM signal to instruct the switch 232 to disconnect thepower supply 246 from the operating coil 220.

In this manner, the operating coil current may be regulated relativelyindependent from the processor 224. Nevertheless, the processor 224 maystill receive the PWM signal from the SR flip-flop 228. As will bedescribed in more detail below, the PWM signal may enable the processor224 to determine when the switching device 218 makes or breaks, as wellas other diagnostic information.

As described above, the operating coil driver circuitry 222 may controloperation of the switching device 218 by controlling the operating coilcurrent. For example, to make (i.e., close) the switching device 218,the operating coil driver circuitry 222 may supply electric power to theoperating coil 220, which magnetizes the operating coil 220. Themagnetized operating coil 220 then attracts the armature 118, oneembodiment of which is depicted in FIG. 8, to close the switching device218. To help illustrate, a profile of the operating coil current 250used to make the switching device 218 is shown in FIGS. 26A and 26B,which is a zoomed in view of FIG. 26A.

As depicted in FIG. 26A, between t0 and t1, current is not supplied tothe operating coil 220. At t1, a small amount of current insufficient toclose the switching device 218 is supplied to the operating coil 220.More specifically, as will be described in more detail below, the smallamount of current may be utilized to measure the temperature (e.g.,actual or relative temperature) of the operating coil 220. Accordingly,the operating coil current 250 between t1 and t2 is generally referredto herein as the “measurement current.” Moreover, the measurementcurrent may also serve to “precharge” the magnetic flux in the operatingcoil 220, thereby reducing amount of current increase to close theswitching device. In this manner, repeatability and/or timing of closingthe switching device 218 may be further improved.

Between t2 to t3, the operating coil current 250 is ramped up from themeasurement current to a level sufficient to close the switching device218. Accordingly, the operating coil current 250 between t3 and t4 isgenerally referred to herein as the “pull-in current.” It should benoted that as in the depicted embodiment, the current is partiallyramped up to an intermediate current level between the measurementcurrent and the pull-in current. In some embodiments, the operating coildriver circuitry 222 may ramp the current to the intermediate currentlevel to further precharge the magnetic flux in the operating coil 220,thereby reducing amount of current increase to close the switchingdevice. Additionally or alternatively, the current may be directlyramped up from the measurement current to the pull-in current.

Upon ramping the operating coil current 250 up to the pull-in current,the armature 118 may begin to move. As the armature 118 moves, theimpedance of the operating coil 220 increases. More specifically, thearmature 118 may behave as both a position variable inductor and as alinear motor and, thus, affect inductance (e.g., impedance) of theoperating coil 220 when in motion. Accordingly, to maintain theoperating coil current 250 at the target level (e.g., pull-in current),the operating coil driver circuitry 222 may increase the amount ofelectric power supplied to the operating coil 220. As described above,this may include increasing the duty cycle of the PWM signal.

By design, at t4, the impedance of the operating coil 220 has increasedto a point where the electric power supplied by the power supply 246 isno longer able to maintain the operating coil current 250 at the pull-incurrent. As depicted, the operating coil current 250 sharply drops.After the switching device 218 makes, the impedance of the operatingcoil 220 returns to normal, thereby enabling the operating coil current250 to return to the pull-in current. More specifically, when thearmature 118 stops moving (e.g., when it hits the yoke 106) inductancegenerated by movement of the armature may dissipate. Accordingly, asdepicted, the operating coil current 250 returns to the pull-in currentat t5, which produces a “V” between t4 and t5.

In fact, as will be described in more detail below, the profile of theoperating coil current 250 (e.g., duration between t4 and t5) may beused as an indication of armature 118 position and, thus, when theswitching device 218 makes. More specifically, at some time between t4and t5, for example at tM, the switching device 218 makes. The drop inthe operating coil current 250 between t4 and t5 is more clearlydepicted in FIG. 26B.

As depicted, after t5, the operating coil current 250 is reduced to acurrent level sufficient to hold the switching device 218 closed. Assuch, the operating coil current 250 after t5 is generally referred toherein as the “hold-in current.” In some embodiments, the operating coilcurrent 250 may be reduced to the hold-in current to reduce the powerconsumption of the switching device 218 and/or ohmic heating of theoperating coil 220.

Based on the above description, the make time of the switching device218 is generally not instantaneous. As used herein, the “make time” isgenerally intended to describe the time between when pull-in current isapplied and when the switching device 218 makes. For example, there is aslight delay between when pull-in current is applied at t3 and when theswitching device 218 actually makes at tM. Accordingly, the operatingcoil driver circuitry 222 may take into account the non-instantaneousnature of the switching device 218 to improve control of the switchingdevice 218, for example, to facilitate making the switching device 218at a specific point on the electric power waveform. To help illustrate,FIG. 27 depicts a source voltage waveform 252 of one phase of electricpower supplied to the switching device 218 from the power source 12.

As described above, to reduce magnitude of inrush current and/or currentoscillation, the switching device 218 may be closed based upon apredicted current zero-crossing (e.g., a point on source waveform 252within a range from slightly before to slightly after the predictedcurrent zero-crossing). As described above, the predicted currentzero-crossing may occur at a line-to-line voltage maximum (e.g., 90°after a line-to-line voltage zero crossing or 60° after aline-to-neutral voltage zero crossing). For example, in the depictedembodiment, the switching device 218 is desired to make at point 254(e.g., a line-to-line voltage maximum). As described above, theswitching device 218 may be closed by setting the operating coil current250 to the pull-in current to attract the armature 118. Accordingly,since the switching device 218 generally does not make instantaneously,the operating coil current 250 may be set to the pull-in current at anearlier time to make the switching device 218 at a tM that correspondswith the point 254.

More specifically, the operating coil current 250 may be controlledbased at least in part on the expected make time of the switching device218. Based on the above described example, the operating coil current250 is set to the pull-in current at t3 to make the switching device 218at tM. In other words, the expected make time 256 of the switchingdevice is the difference between t3 and tM. The operating coil current250 may then be controlled based at least in part on the expected maketime 256 of the switching device 218 (e.g., difference between t3 andtM).

One embodiment of a process 258 that may be used to make the switchingdevice 218 at a specific point on an electric power waveform is shown inFIG. 28. The process 258 may be implemented via computer-readableinstructions stored in the tangible non-transitory memory 226, 20, 46,and/or other memories and executed via processor 224, 19, 45, and/orother control circuitry. Generally, the process 258 includes determininga desired time to make the switching device 218 (process block 260),determining an expected make time of the switching device 218 (processblock 262), and applying the current profile to make the switchingdevice 218 at the desired time (process block 264). Additionally, theprocess 258 optionally includes determining when the switching device218 makes (process block 266).

In some embodiments, the processor 224 may determine the desired time tomake the switching device 218 (process block 260). As described above,the switching device 218 may be closed a specific point on the electricpower waveform to minimize in-rush current, current transients, currentoscillations and/or torque oscillations. Accordingly, in someembodiments, the processor 224 may determine that the specific pointcorresponds to a predicted current zero-crossing and/or a line-to-linevoltage maximum. The processor 224 may then determine the timeassociated with the specific point.

As can be appreciated, each step in process 258 is generally notinstantaneous. Accordingly, the desired time to make the switchingdevice 218 may be selected to provide sufficient time to completeprocess 258. In other words, the desired time to make may not alwayscorrespond with the first subsequent predicted current zero-crossing.Additionally, in some embodiments, a user may instruct the operatingcoil driver circuitry 222 to close the switching device 218 as soon aspossible independent of the electric power waveform and the processor224 may determine the desired time to make accordingly.

The processor 224 may then determine the expected make time 256 of theswitching device 218 (process block 262). The make time of the switchingdevice 218 may be affected by various operational parameters, such astemperature. As will be described in more detail below, the temperature(e.g., actual temperature or relative temperature) may be determined viaimpedance of the operating coil 220 or other methods, such as atemperature sensor. Accordingly, the processor 224 may determine thevarious operational parameters, for example via sensors 22 or themeasurement current, to determine the expected make time 256 of theswitching device 218.

More specifically, in some embodiments, the processor 224 may input theoperational parameters into a make time look-up-table (LUT) that relatesthe determined operational parameters to an expected make time 256. Forexample, when a specific temperature is input to the make time LUT, theLUT may output an expected make time 256. Although the describedembodiments describe the used of look-up tables (LUTs), in otherembodiments, the same results may be achieved by calculations performedby the processor 224 using various algorithms or a combination ofalgorithms and LUTs. Additionally, since the make time LUT, may bedetermined during normal operations, the processor 224 may adjust forany other known operational parameters that may affect the expected maketime 256, such as a filtering delay, device wear, and/or otherenvironmental conditions.

In some embodiments, the make time LUT may be based on empirical tests,such as past make times. For example, in some embodiments, amanufacturer may conduct tests on the particular switching device 218 ora comparable switching device 218 to determine the make time of theswitching device 218 under the various operational parameters andpopulate the make time LUT accordingly. Additionally, when the switchingdevice 218 is put into commission, the switching device 218 may run atesting sequence to determine when the switching device 218 makes underthe various sets of operational parameters to calibrate the make timeLUT.

Since the techniques described herein are based on previous operations,it is emphasized that the single-pole, single current-carrying pathswitching device 218 described above is designed to have highlyrepeatable and, thus, highly predictable operation. As such, the maketime LUT enables the processor 224 to determine, with a reasonablecertainty, the make time of the switching device 218 based on the maketime of the switching device 218 previously under similar parameters.Nevertheless, it should be appreciated that the techniques may also beused for other types of switching devices, such as a multi-poleswitching device.

Based on the expected make time, the current profile may be applied tothe switching device 218 to make the switching device 218 at thedetermined time (process block 264). For example, the current profilemay set the operating coil current 250 to the pull-in current. Morespecifically, the processor 224 may determine when to apply the currentprofile to the switching device 218 to make at the desired time. In someembodiments, the processor 224 may determine a specific time to applythe current profile by subtracting the expected make time 256 from thedesired time to make. For example, subtracting the expected make time256 from tM (e.g., desired time to make) results in t3 (e.g., thespecific time to apply the current profile). Accordingly, as describedabove, the current profile is applied to the switching device 218 at t3.

Additionally, as described above, the operating coil current 250 may beramped up to an intermediate level before the pull-in current.Accordingly, in such embodiments, the processor 224 may determine whento ramp up to the intermediate level. For example, the processor 224 maydetermine a specific time to ramp up to the intermediate level bysubtracting a ramp up period (e.g., time between t2 and t3) from t3.

After the current profile is applied, the processor 224 may optionallydetermine when the switching device 218 makes (process block 266). Morespecifically, determining when the switching device 218 makes may enabledetermining the actual make time of the switching device 218.

As described above, the make time LUT may be based at least in part onpast make operations. However, the make time of the switching device 218may gradually change over time. For example, as the switching device 218ages, the force provided by the spring 110 that resists closing theswitching device 218 may gradually decrease, which may gradually reducethe make time of the switching device 218. Additionally, as contactmaterial wears away, the distance the switching device 218 moves toclose may increase and/or debris may building up causing friction, whichmay gradually increase the make time of the switching device 218.

Accordingly, determining the actual make time may facilitate calibratingand/or updating the make time LUT to better account for operationalchanges in the switching device. In fact, as will be described in moredetail below, keeping track of the actual make times may facilitateperforming diagnostics on the switching device 218. For example, if themake time of the switching device 218 is different than expected, theprocessor 224 may identify that the switching device 218 may beobstructed in some way or suffering from some other anomalous condition.

In some embodiments, the processor 224 may utilize the PWM signal todetermine when the switching device 218 makes. More specifically, asdescribed above, the PWM signal output by the SR flip-flop 228 is fedback to the processor 224. Based on the duty cycle of the PWM signal,the processor 224 may determine duration of the drop in the operatingcoil current (e.g., duration between t4 and t5), which may be directlyrelated to when the switching device 218 makes.

To help illustrate, FIG. 29 depicts the trigger signal 244 output by theprocessor 224 and the PWM signal 268 input to the processor 224. Asdescribed above, the trigger signal 244 is input to the SR flip-flop 228to facilitate generating the PWM signal 268 by periodically attemptingto set the SR flip-flop 228 (e.g., make the PWM signal 268 high). Morespecifically, when comparator 230 determines that the operating coilcurrent 250 is lower than the target and the trigger signal 244 is high,the SR flop-lop 228 outputs a high PWM signal 268 instructing the switchto turn on, thereby supply electric power from the power supply 246 tothe operating coil 220. On the other hand, when the comparator 230determines that the operating coil 250 is not lower than the target, theSR flop-lop 228 outputs a low PWM signal 268 instructing the switch toturn off, thereby disconnecting electric power from the operating coil220. In other words, the PWM signal 268 may turn on the switch 232 andthe switch 232 may remain on until the comparator 230 determines thatthe operating coil current 250 is greater than the reference voltage(i.e., Vref). At that point, the comparator 230 may reset the SRflip-flop 282, thereby turning off the switch 232.

As described above, between t3 and t4, the operating coil current 250 isset at the pull-in current. Accordingly, in the depicted embodiment,supplying electric power to the operating coil 220 based on the PWMsignal 268 depicted between t3 and t4 may maintain the operating coilcurrent 250 at the pull-in current. Additionally, as described above,after the armature 118 begins to move, the impedance of the operatingcoil 220 begins to increase. Accordingly, as depicted, the duty cycle ofthe PWM signal 268 gradually increases between t3 and t4 to compensatefor the impedance increase and maintain the operating coil current 250at the pull-in current.

In other words, the SR flip-flop 228 may continue to increase the dutycycle of the PWM signal 268 in an attempt to maintain the operating coilcurrent 250 at the pull-in current. Accordingly, the sharp drop inoperating coil current 250 between t4 and t5, described above, indicatesthat even the maximum electric power output by the power supply 246 isinsufficient to maintain the operating coil current 250 at the pull-incurrent. Thus, as depicted, the duty cycle of the PWM signal 268 isincreased to 100% between t4 and t5. As such, the processor 224 maydetermine the duration between t4 and t5 by determining duration the PWMsignal 268 is at 100% duty cycle.

Accordingly, as will be described in more detail below, the power supply246, the magnitude of the pull-in current, and/or the coil design may bedetermined to produce the sharp operating coil drop between t4 and t5.It should be noted that 100% duty cycle is merely intended to beillustrative. In other embodiments, the processor 224 may determine themake time and/or when the switching device makes by determining durationduty cycle of the PWM signal 268 is at another predetermined level.

As described above, the duration between t4 and t5 (e.g., when the PWMsignal 268 is at 100% duty cycle) may be utilized to determine when theswitching device 218 makes. One embodiment of a process 270 to determinewhen the switching device 218 makes is shown in FIG. 30. The process 270may be implemented via computer-readable instructions stored in thetangible non-transitory memory 226, 20, 46 and/or other memories andexecuted via processor 224, 19, 45 and/or other control circuitry.Generally, the process 270 includes determining when the PWM signalreaches 100% duty cycle (process block 272), determining when the PWMsignal duty cycle falls below 100% (process block 274), determining theduration the PWM signal is at 100% duty cycle (process block 276),determining when the switching device makes (process block 278), andupdating the LUT with the determined make time (process block 280).

In some embodiments, the processor 224 may determine when the duty cycleof the PWM signal 268 reaches 100% (process block 272). As describedabove, the duty cycle reaching 100% may indicate that the maximum amountof electric power is being supplied to the operating coil 220, whichcorresponds with when the operating coil current 250 begins to drop(e.g., at t4). Additionally, the processor 224 may determine when theduty cycle of the PWM signal 268 falls below 100% (process block 274).As described above, the duty cycle falling below 100% may indicate thatthe armature 119 is no longer moving and the switching device 218 isclosed, which correspond with when the operating coil current 250returns to the pull-in current (e.g., at t5). Accordingly, based on whenthe duty cycle reaches 100% and when the duty cycle falls below 100%,the processor 224 may determine the duration the duty cycle of the PWMsignal 268 remains at 100%, which may indicate duration of the drop inthe operating coil current 250 (e.g., duration between t4 and t5)(process block 276).

Based on the duration the duty cycle is at 100%, the processor 224 maydetermine when the switching device 218 makes (process block 278). Morespecifically, a relationship between tM and the duration between t4 andt5 may be defined based on empirical testing (e.g., historical data). Insome embodiments, the historical data may define that tM occurs at acertain percentage between t4 and t5. For example, the historical datamay define that tM occurs at a time 30% between t4 and t5. In fact, insome embodiments, the switching device 218 may be periodicallyrecalibrated to determine the relationship between tM and the durationbetween t4 and t5, for example, using a high speed camera and/or currentsensors.

Similar to the make time LUT, a manufacturer of the switching device 218may conduct tests on the particular switching device 218 or a comparableswitching device 218 to determine when tM occurs in relation to theduration of t4 to t5. Additionally, it is again emphasized that thesingle-pole, single current-carrying path switching device 218 describedabove is designed to have a highly repeatable and, thus, highlypredictable, operation. In other words, the defined relationship betweentM and the duration of t4 to t5 enables the processor 224 to determine,with a reasonable certainty, when the switching device 218 makes.

Additionally or alternatively, when the switching device 218 makes maybe verified by measuring when current begins to flow through theswitching device 218. For example, a sensor 22 may be placed between theswitching device 218 and the load to feed back a signal indicating thata current is flowing. Thus, the processor 224 or other control circuitrymay verify when the switching device 218 makes. Other techniques, suchas high speed cameras, auxiliary contacts, optical or magnetic positionsensors, and/or flux detectors, may also be used to verify when theswitching device 218 makes.

Furthermore, in some embodiments, the instant the switching device 218closes may be determined based at least in part on other characteristicsthe operating coil current 250, such as an inflection in the currentwaveform. More specifically, when the switching device 218 closes, thebiasing spring 152 may be added to the load seen by the armature 118(e.g., magnetic system), thereby causing the armature 118 to slow downand causing an inflection in the operating coil current 250. In someembodiments, the verification may be performed at a later time and usedto calibrate the make time LUT.

The processor 224 may then update the make time LUT with the determinedmake time (process block 280). More specifically, the processor 224 maydetermine the make time based on the time difference between when thepull-in current is applied (e.g., at t3) and when the switching devicemakes (e.g., at tM). As described above, updating the make time LUT withthe determined make time may enable the operating coil driver circuitry222 to compensate for operational changes in the switching device 218 aswell as perform diagnostics on the switching device 218.

In addition to controlling the make operation of the switching device218, the operating coil driver circuitry 222 may be used to control thebreak (i.e., open) operation of the switching device 218. For example,to break the switching device 218, the operating coil driver circuitry222 may reduce electric power to the operating coil 220, which reducesthe magnetic force generated by the operating coil 220 to hold theswitching device 218 closed. Accordingly, the spring 110 may overcomethe magnetic force generated by the operating coil 220 and open theswitching device 218. To help illustrate, the operating coil current 250and the target operating coil current 282 to break the switching device218 are shown in FIG. 31.

As depicted in FIG. 31, before t6, the operating coil current 250 isgenerally set at the target operating coil current 282. Morespecifically, as described above, the operating coil driver circuitry222 may adjust the operating coil current 250 by connecting anddisconnecting electric power supplied from the power supply 246 from theoperating coil 220. In some embodiments, the operating coil current 250may be set at the hold-in current.

At t6, the target operating coil current 282 is reduced to a levelinsufficient to hold the switching device 218 closed. As will bedescribed in more detail below, the target operating coil current 282after t6 may be utilized to determine when the switching device 218breaks. Accordingly, the target operating coil current after t6 isgenerally referred to herein as the “break current.” Initially when thetarget operating coil current is reduced to the break current at t6, theoperating coil current 250 is higher than the target and electric poweris disconnected from the operating coil 220. More specifically, asdepicted, the operating coil current 250 gradually decreases as theoperating coil 220 dissipates energy stored in its magnetic field viathe flyback diode 234. In other embodiments, the flyback diode 234 maybe connected between resistor 238 and ground. Additionally, in otherembodiments, the flyback diode 234 may be replaced with an activedevice, such as a field effect transistor (FET).

As the operating coil current 250 continues to decrease, the magneticforce produced by the operating coil 220 will no longer be sufficient tohold the switching device 218 closed, thereby causing the switchingdevice 218 to begins to move (e.g., open). Additionally, the collapse ofthe magnetic field collapses may generate (e.g., induce) a current inthe operating coil 220 due to back electromotive force (EMF). Morespecifically, the back EMF may be caused by the line of flux beingdragged along the armature 118 and the coil windings 112 as theswitching device 218 opens. Accordingly, when the switching device 218breaks may be determined by detecting when the current is generated inthe operating coil 220.

As described above, the operating coil current 250 may graduallydecrease as the operating coil 220 dissipates the energy stored in itsmagnetic field. In other words, if electric power is not reconnected tothe operating coil 220, the generated current may be determined byidentifying the minimum in the operating coil current 250. As depicted,the operating coil current 250 is maintained at the target operatingcoil current 282 between t7 and t8. Accordingly, the minimum operatingcoil current 250 is at some time between t7 and t8. In other words, theswitching device 218 breaks at some time between t7 and t8, for exampleat tB. Thus, similar to determining when the switching device 218 makesthe duration between t7 and t8 may be used with historical data and/ordesign attributes of the switching device 218 to determine when theswitching device 218 breaks (e.g., at tB).

As depicted, at t8, the generated current in the operating coil 220causes the operating coil current 250 to increase above the targetoperating coil current 282 (e.g., break current). In other words, eventhough the power supply 246 is disconnected from the operating coil 220,the operating coil current 250 rises above the target operating coilcurrent 282. Accordingly, to facilitate determining the duration betweent7 and t8, the break current is set slightly below the current inducedin the operating coil 220 by the movement of the armature 118.Additionally, as depicted, after t9, the operating coil current 250 ismaintained at the break current.

Similar to the make time, based on the above description, the break timeof the switching device 218 is generally not instantaneous. In otherwords, there is a slight delay between when the target operating coilcurrent 282 is reduced to the break current (e.g., at t6) and when theswitching device 218 actually breaks (e.g., at tB). As used herein, the“break time” is generally intended to describe that time period.Accordingly, the operating coil driver circuitry 222 may take intoaccount the non-instantaneous nature of the switching device 218 toimprove control of the switching device 218, for example, to break theswitching device 218 at a specific point on the electric power waveform.To help illustrate, FIG. 32 depicts a switching device current waveform284 of electric power conducted by the switching device 218.

As described above, to reduce electrical arcing, the switching device218 may be opened based upon a current zero-crossing (e.g., a point onthe switching device current waveform 284 within a range from slightlybefore to the current zero-crossing). For example, in the depictedembodiment, the switching device 218 is desired to break at a currentzero-crossing at point 286. As described above, the switching device 218may be opened by setting the operating coil current 250 to the breakcurrent to enable the spring 110 to overpower the magnetic forcegenerated by the operating coil 220. Accordingly, since the switchingdevice 218 generally does not break instantaneously, the operating coilcurrent 250 may be set to the break current at an earlier time to breakthe switching device 218 at tB, which corresponds with the point 286.

More specifically, the operating coil current 250 may be controlledbased at least in part on the expected break time of the switchingdevice 218. Based on the above described example, the target operatingcoil current 282 is set to the break current at t6 to break theswitching device 218 at tB. In other words, the expected break time 288of the switching device is the difference between t6 and tB.

One embodiment of a process 290 that may be used to break the switchingdevice 218 at a specific point on an electric power waveform is shown inFIG. 33. The process 290 may be implemented via computer-readableinstructions stored in the tangible non-transitory memory 226, 20, 46and/or other memories and executed via processor 224, 19, 45 and/orother control circuitry. Generally, the process 290 includes determininga desired time to break the switching device 218 (process block 292),determining an expected break time of the switching device 218 (processblock 294), and applying the current profile to break the switchingdevice 218 at the desired time (process block 296). Additionally, theprocess 290 optionally includes determining when the switching device218 breaks (process block 298).

In some embodiments, the processor 224 may determine the desired time tobreak the switching device (process block 292). As described above, theswitching device 218 may be opened based on a current-zero crossing ofthe conducted electric power. Additionally, the processor 224 maydetermine the time associated with the specific point. Accordingly, insome embodiments, the processor 224 may determine the desired time tobreak the switching device 218 based on a subsequent currentzero-crossing.

As can be appreciated, each step in process 290 may generally benon-instantaneous. Accordingly, in some embodiments, the desired time tobreak the switching device 218 may be selected to provide sufficienttime to complete process 290. In other words, the desired time may notalways correspond with the first subsequent zero-crossing. In otherembodiments, it may be desired to break the switching device 218 as soonas possible independent of the electric power waveform and the processor224 may determine the desired time to break accordingly.

The processor 224 may then determine the expected break time 288 of theswitching device 218 (process block 294). Similar to the make time, thebreak time of the switching device 218 may be affected by variousoperational parameters, such as temperature, wear, fatigue, and/ordebris. As will be described in more detail below, the temperature(e.g., actual temperature or relative temperature) may be determined viaimpedance of the operating coil 220 or other methods, such as atemperature sensor. Accordingly, the processor 224 may determine thevarious operational parameters, for example via sensors 22 or thehold-in current, to determine the expected make time 256 of theswitching device 218.

More specifically, the processor 224 may input the operationalparameters into a break time look-up-table (LUT) that relates thedetermined operational parameters to an expected break time 288. Forexample, when a specific temperature is input to the break time LUT, theLUT may output an expected break time 288. Additionally, the processor224 may adjust for any other known offsets that may affect the expectedbreak time 288, such as a filtering delay. Although the describedembodiments describe the used of look-up tables (LUTs), in otherembodiments, the same results may be achieved by calculations performedby the processor 224 using various algorithms or a combination ofalgorithms and LUTs. Additionally, since the break time LUT, may bedetermined during normal operations, the processor 224 may adjust forany other known operational parameters that may affect the expected maketime 256, such as a filtering delay, device wear, and/or otherenvironmental conditions.

Similar to the make time LUT, the break time LUT used to determineexpected break time may be based on empirical tests, such as past breaktimes. For example, in some embodiments, a manufacturer may conducttests on the particular switching device 218 or a comparable switchingdevice 218 to determine the break time of the switching device 218 underthe various operational parameters and populate the break time LUTaccordingly. Additionally, when the switching device 218 is put intocommission, the switching device 218 may run a testing sequence todetermine when the switching device 218 breaks under the presentparameters and calibrate the break time LUT.

Since the techniques described herein are based on previous operations,it is again emphasized that the single-pole, single current-carryingpath switching device 218 described above is designed having a highlyrepeatable and thus highly predictable operation. In other words, thebreak time LUT enables the processor 224 to determine, with a reasonablecertainty, the break time of the switching device 218 based on the breaktime of the switching device 218 previously under similar parameters.Nevertheless, it should be appreciated that the techniques may also beused for other types of switching devices, such as a multi-poleswitching device.

Based on the expected break time, the current profile may be applied tothe switching device 218 to break the switching device 218 at adetermined time (process block 296). More specifically, the processor224 may determine when to apply the current profile to the switchingdevice 218 to break at the desired time. In some embodiments, theprocessor 224 may determine a specific time to apply the current profileby subtracting the expected break time 288 from the desired time tomake. For example, subtracting the expected break time 288 from tB(e.g., desired time to make) results in t6 (e.g., the specific time toapply the current profile). Accordingly, as described above, the targetoperating coil current 282 is set at the hold-in current (e.g., currentprofile) at t6. It should be noted that it may be desirable to break theswitching device 218 slightly before the current zero-crossing tominimize the chances of breaking after the zero-crossing.

After the current profile is applied, the processor 224 may optionallydetermine when the switching device 218 breaks (process block 298). Morespecifically, determining when the switching device 218 makes may enabledetermining the actual make time of the switching device 218.

As described above, the break time LUT may be based at least in part onpast break operations. However, the break time of the switching device218 may gradually change over time. For example, as the switching device218 ages, the force provided by the spring 110 that opens the switchingdevice 218 may gradually decrease, which may gradually increase thebreak time of the switching device 218. Additionally, as contactmaterial wears away, the distance the switching device 218 moves to openmay increase and/or debris may build up causing friction, which maygradually increase the break time of the switching device 218.

Accordingly, determining the actual break time may facilitatecalibrating and/or updating the break time LUT to better account foroperational changes in the switching device. In fact, as will bedescribed in more detail below, keeping track of the actual break timesmay facilitate performing diagnostics on the switching device 218. Forexample, if the break time of the switching device 218 is different thanexpected, the processor 224 may identify that the switching device 218may be obstructed in some way or suffering from some other anomalouscondition.

In some embodiments, the processor 224 may utilize the PWM signal todetermine when the switching device 218 makes. More specifically, asdescribed above, the PWM signal output by the SR flip-flop 228 is fedback to the processor 224. Based on the duty cycle of the PWM signal,the processor 224 may determine in duration the operating coil currentis below the break current (e.g., duration between t4 and t5), which maybe directly related to when the switching device 218 breaks.

To help illustrate, FIGS. 34A and 34B depicts the trigger signal 244output by the processor 224 and the PWM signal input 268 to theprocessor 224. More specifically, FIG. 34A depicts the PWM signal 268output by a standard SR flip-flop and FIG. 34B depicts the PWM signal268 output by an SR flip-flop that is set each time the S terminal goeshigh.

As described above, the trigger signal 244 is input to the SR flip-flop228 to facilitate generating the PWM signal 268 by periodicallyattempting to set the SR flip-flop 228 (e.g., make the PWM signal 268high). More specifically, when comparator 230 determines that theoperating coil current 250 is lower than the target and the triggersignal 244 is high, the SR flop-lop 228 outputs a high PWM signal 268instructing the switch to turn on, thereby supply electric power fromthe power supply 246 to the operating coil 220. On the other hand, whenthe comparator 230 determines that the operating coil current 250 is notlower than the target, the SR flop-lop 228 outputs a low PWM signal 268instructing the switch to turn off, thereby disconnecting electric powerfrom the operating coil 220. In other words, the trigger signal 244 mayturn on the switch 232 and the switch 232 may remain on until thecomparator 230 determines that the operating coil current 250 is greaterthan the reference voltage (i.e., Vref). At that point, the comparator230 may reset the SR flip-flop 282, thereby turning off the switch 232.

As described above, between t6 and t7, the operating coil current 250 ishigher than the target operating coil current 282. Thus, the comparator230 will input a high signal to the R terminal of the SR flip-flop 228.In other words, in a standard SR flip-flop, the PWM signal 268 will below regardless of the input at the S terminal. Accordingly, as depicted,duty cycle of the PWM signal 268 between t6 and t7 is 0%. In otherwords, the power supply 246 is disconnected from the operating coil 220as the energy stored in the operating coil 220 is gradually dissipated.

Additionally, as described above, the SR flip-flop 228 may increase theduty cycle of the PWM signal 268 to maintain the operating coil current250 at the target operating coil current 282. Thus, when the operatingcoil current 250 begins to drop below the target operating coil current282 between t7 and t8, electric power is supplied to the operating coil220 to maintain the operating coil current 250 at the target operatingcoil current 282. Accordingly, in the depicted embodiment, the PWMsignal 268 has a non-zero duty cycle to maintain the operating coilcurrent 250 at the break current. As such, the process 224 may determinethe duration between t7 and t8 by determining the duration the PWM is ata non-zero duty cycle.

Furthermore, as described above, when the armature 118 begins to move, acurrent is generated in the operating coil 220, which causes theoperating coil current 250 to rise above the target operating coilcurrent 282 between t8 and t9. Since the operating coil current 250 ishigher than the target operating coil current 282, electric power isdisconnected from the operating coil 220. Accordingly, as depicted, theduty cycle of the PWM signal 268 between t8 and t9 is 0%.

Additionally, as described above, after t9, the generated currentdecreases below the target operating coil current 282 and the operatingcoil current 250 is maintained at the target operating coil current 282by connecting and disconnecting electric power. Accordingly, in thedepicted embodiment, the PWM signal 268 has a non-zero duty cycle aftert9 to maintain the operating coil current 250 at the break current.Thus, it may be determined that the armature 118 is no longer movingwhen the duty cycle again goes non-zero (e.g., at t9).

The embodiment of the PWM signal 268 shown in FIG. 34B is similar to theone shown in FIG. 34A with the distinction that the SR flip-flop 228used to generate the PWM signal 268 shown in FIG. 34B goes high wheneverthe input to the S terminal goes high. In other words, as depicted,between t6 and t7, since the operating coil current 250 is higher thanthe target operating coil current 282, the duty cycle of the PWM signal268 is at its minimum. In some embodiments, the minimum duty cycle maybe equal to the duty cycle of the trigger signal 244. Accordingly, theduration between t7 and t8 may be determined by the duration the dutycycle of the PWM signal 268 is above its minimum.

In fact, since minimum duty cycle is non-zero, the PWM signal 268 mayinstruct the switch 232 to turn on for at least the duty cycle of thetrigger 244. As such, a minimum amount of electric power may be suppliedto the operating coil 220. In some embodiments, supplying a positiveminimum amount of electric power to the operating coil 220 mayfacilitate stabilizing oscillations in the operating coil current 250,thereby providing a more accurate determination of the duration theoperating coil current 250 is below the break current.

Similarly, as depicted, between t8 and t9, since the operating coilcurrent 250 is higher than the operating current target 282 due to thecurrent generated by the movement of armature 118, the duty cycle of thesignal 268 is again at its minimum. More specifically, the duty cycle ofthe PWM signal 268 may again be equal to the duty cycle of the triggersignal 244. Accordingly, it may be determined that the armature 118 isno longer moving when the duty cycle of the PWM signal 268 increasesabove its minimum (e.g. after t9).

Although either embodiment of the SR flip-flop 228 may be utilized. Tosimplify the following discussion, the embodiment shown in FIG. 34A willbe utilized. It should be noted that one of ordinary skill in art willbe able to easily convert between looking for a minimum duty cycle, a 0%duty cycle, and another predetermined duty cycle.

As described above, the duration between t7 and t8 (e.g., when the PWMsignal 268 is non-zero) may be utilized to determine when the switchingdevice breaks. One embodiment of a process 300 is shown in FIG. 35. Theprocess 300 may be implemented via computer-readable instructions storedin the tangible non-transitory memory 226, 20, 46 and executed viaprocessor 224, 19, 45 and/or other control circuitry. Generally, theprocess 300 includes determining when the PWM signal reaches 0% dutycycle (process block 302), determine when the PWM signal duty cycle isnon-zero (process block 304), determining when the PWM signal againreaches 0% duty cycle (process block 306), determining duration the PWMsignal duty cycle is non-zero (process block 308), determining when theswitching device breaks (process block 310), and updating the LUT withthe determined break time (process block 312).

In some embodiments, the processor 224 may determine when the duty cycleof the PWM signal 268 reaches 0% (process block 302). As describedabove, the duty cycle falling to 0% (e.g., minimum level) may indicatethat the operating coil 220 is dissipating energy stored in its magneticfield, but still above the break current. In other words, the armature118 has not begun to move because the minimum of the operating coilcurrent 250 has not yet been reached.

Additionally, the processor 224 may determine when the duty cycle of thePWM signal 268 is non-zero (process block 304). As described above, theduty cycle increasing to non-zero (e.g., above minimum level) mayindicate that electric power is being supplied to the operating coil220, which corresponds with when the operating coil current 250 beginsto fall below the target operating coil current 282 (e.g., at t7).Furthermore, the processor 224 may determine when the duty cycle of thePWM signal 268 again goes to 0% (process block 306). As described above,the duty cycle again falling to 0% (e.g., minimum level) may indicatethat the operating coil current 250 is higher than the target operatingcoil current 282 due to the induced current in the operating coil 220(e.g., at t8). In other words, at this point, the armature 118 is inmotion and, thus, the switching device 218 has opened at some timebetween t7 and t8. Accordingly, based on when the duty cycle is non-zeroand when the duty cycle again goes to 0%, the processor 224 maydetermine the duration the duty cycle of the PWM signal 268 is non-zero,which may indicate the operating coil current 250 is below the breakcurrent (e.g., duration between t7 and t8) (process block 308).

Based on the duration the PWM signal is non-zero, the processor 224 maydetermine when the switching device 218 breaks (process block 310). Morespecifically, a relationship between tB and the duration between t7 andt8 may be defined based on empirical testing (e.g., historical data). Insome embodiments, the historical data may define that tB occurs at acertain percentage between t7 and t8. For example, the historical datamay define that tB occurs at 45% between t7 and t8. In fact, in someembodiments, the switching device 218 may be periodically recalibratedto determine the relationship between tB and the duration between t7 andt8, for example, using a high speed camera and/or current sensors.

Similar to the break time LUT, a manufacturer of the switching device218 may conduct tests on the particular switching device 218 or acomparable switching device 218 to determine when tB occurs in relationto the duration between t7 to t8. Additionally, it is again emphasizedthat the single-pole, single current-carrying path switching device 218described above is designed having a highly repeatable and thus highlypredictable operation. In other words, the defined relationship betweentB and the duration of t7 to t8 enables the processor 224 to determine,with a reasonable certainty, when the switching device 218 breaks.

Additionally or alternatively, when the switching device 218 breaks maybe verified by measuring when current ceases to flow through theswitching device 218. For example, a sensor 22 may be placed between theswitching device 218 and load to feed back a signal indicating that acurrent has stopped flowing. Thus, the processor 224 or other controlcircuitry may verify when the switching device 218 breaks. Othertechniques, such as a high speed camera, may also be used to verify whenthe switching device 218 breaks. In some embodiments, the verificationmay be performed at a later time and used to calibrate the break timeLUT.

The processor 224 may then update the break time LUT with the determinedbreak time (process block 312). More specifically, the processor 224 maydetermine the break time based on the time difference between when thetarget operating coil current 282 is set at the break current (e.g., att6) and when the switching device breaks (e.g., at tB). As describedabove, updating the break time LUT with the determined break time mayenable the operating coil driver circuitry 222 to compensate foroperational changes in the switching device 218 as well as performdiagnostics on the switching device 218.

In addition to utilizing the PWM signal 268, in some embodiments, theprocessor 224 may determine when the switching device makes or breaksbased directly on the output of the comparator 230. More specifically,in such embodiments, the output of comparator 230 may be input to theprocessor 224, as depicted in FIG. 36.

As such, the processor 224 may determine whether the operating coilcurrent 250 is higher or lower than a target level based on the outputof the comparator 230. As described above, the processor 224 may outputa reference voltage (e.g., Vref) that corresponds with the targetoperating coil current 282. Accordingly, the processor 224 may determinewhen the operating coil current 250 is below the target operating coilcurrent 282 when the output of the comparator 230 is low. On the otherhand, the processor 224 may determine when the operating coil current250 is above the target operating coil current 282 when the output ofthe comparator 230 is high. In fact, the processor 224 may adjust thetrigger signal 224 to better handle oscillations in the operating coilcurrent 250, for example, by adjusting the duty cycle to adjust minimumamount of electric power be supplied to the operating coil 220.

In fact, such an embodiment of the operating coil driver circuitry 222may enable electric power to be completely disconnected during a breakoperation. More specifically, since the processor 224 may determine whenthe operating coil current 250 falls below the break current (e.g.,duration between t7 and t8) directly from the comparator 230, theoperating coil driver circuitry 222 may allow the operating coil current250 to dissipate naturally. In other words, the duty cycle of the PWMsignal 268 may be set to 0% to disconnect electric power from theoperating coil 220. For example, the processor 224 may cease the triggersignal 244 input to the S terminal of the SR flip-flop 228, which causesthe PWM signal 268 to remain low and disconnects the power supply 246.In some embodiments, disconnecting the power supply 246 may reduce thepower consumption of the operating coil driver circuitry 222. Similarly,the operating driver circuitry 222 may also enable the processor 224 todetermine when the operating coil current 250 falls below the pull-incurrent (e.g., duration between t4 and t5) directly from the comparator230.

As described above, to facilitate determining when the switching device218 makes, the operating coil current 250 drops because the power supply246 is no longer sufficient to maintain the operating coil current 250at the pull-in current due to the impedance increase in the operatingcoil 220. More specifically, as the operating coil 220 draws electricpower from the DC bus 248, the voltage on the DC bus 248 (e.g., busvoltage) may begin to droop because electric power is being drawn fromthe power supply 246 faster than it is being replenished by the powersource 12. To help illustrate, FIG. 37 depicts the bus voltage 314during a make operation.

As described above, the operating coil current 250 begins to be rampedup to the pull-in current at t2. As such, the electric power drawn bythe operating coil 220 increases to maintain the operating coil current250 at the target current (e.g., pull-in current). However, as depicted,the bus voltage 314 begins to sag at t2. The bus voltage 314 continuesto sag until some time after the switching device 218 makes at tM. Inother words, the power supply 246 may set the bus voltage 314 such thatit is sufficient to maintain the operating coil current 250 at thepull-in current without sagging.

Based on the techniques described herein, when the switching device 218makes may be determined based on the duration of the operating coilcurrent 250 drop (e.g., duration between t4 and t5). Thus, it isimportant to clearly define when the PWM signal 268 is at 100% dutycycle. However, the bus voltage 314 may affect this determinationbecause the bus voltage 314 affects the electric power supplied to theoperating coil 220 to make the switching device 218. Additionally, asthe switching device 218 makes, the impedance of the operating coil 220may increase. In other words, a higher the bus voltage 314 may enablemore electric power to be supplied, thereby decreasing the make time andincreasing rate of impedance change. On the other hand, a lower busvoltage may enable less electric power to be supplied, therebyincreasing the make time and decreasing the rate of impedance change.

Accordingly, the bus voltage 314 may be adjusted so that sufficientelectric power may be supplied to operating coil 220 make the switchingdevice 218 while also causing a drop form the 100% duty cycle.Additionally, the bus voltage 314 may be adjusted to control theduration and/or aggressiveness of the drop in operating coil current250. For example, when the bus voltage 314 is higher, the drop inoperating current may be narrower shallower. On the other hand, when thebus voltage 314 is lower, the drop in the operating current may belater, wider, and deeper.

Thus, duration of the operating coil current drop may be adjusted toenable the duration the PWM signal 268 is at 100% duty cycle to beeasily detected. For example, by reducing the bus voltage 314, theduration of the current drop may be increased. Additionally, theaggressiveness of the drop may be adjusted to ensure that the durationof the operating coil current drop corresponds with the duration the PWMsignal 268 is at 100% duty cycle. More specifically, when the slope ofthe operating coil current 250 entering or exiting the drop is lessaggressive, the possibility of the PWM signal duty cycle dropping below100% while the operating coil current 250 is still in the dropincreases. Such stray pulses may make determining the duration of thecurrent drop more difficult because it is unclear at what instant theoperating coil 250 enters or exits the drop. Accordingly, for example,the bus voltage 314 may be increased to increase the aggressiveness ofthe operating coil current drop.

Additionally, the magnitude of the pull-in current that the operatingcoil driver circuitry 222 attempts to maintain the operating coilcurrent 250 may also affect the drop in the operating coil current 250.More specifically, when the pull-in current is higher, the electricpower supplied is higher, thereby decreasing the make time whileincreasing the power consumption of the switching device 218. In otherwords, a higher pull-in current may increase rate of impedance changeand, thus, cause a more dramatic drop in the bus voltage 314. On theother hand, when the pull-in current is lower, the electric powersupplied may be lower, thereby increasing the make time while decreasingpower consumption of the switching device 218. In other words, a lowerpull-in current may decrease rate of impedance change and, thus, cause aless dramatic drop in the bus voltage 314.

Accordingly, an optimal balance between the bus voltage 314 and thepull-in current may be determined to improve detection of when theswitching device 218 makes. Moreover, the optimal balance may further beadjusted when multiple switching devices 218 make. For example, asdescribed above, a first switching device 218 may connect a first phaseof electric power and a second switching device 218 may connect a secondphase of electric power to an electrical motor 24 at a first time (e.g.,based upon a predicted current zero-crossing). A third switching device218 may then connect a third phase of electric power at to theelectrical motor 24 at a second time. To help illustrate, the first andthe second switching device 218 may close at tM and the third switchingdevice 218 may close at tM′, as depicted in FIG. 33.

As depicted, the bus voltage 314 at tM may differ from the bus voltageat tM′. As described above, the bus voltage 314 during a make operationmay affect the operating coil current 250 drop used to detect when theswitching device 218 makes. Such effects may be compounded with regardto the third switching device 218 because the effects of the first andsecond switching device 218 are integrated through to tM′. For example,as depicted, the electric power drawn by the first and second switchingdevices 218 to make at tM sags the bus voltage 314. After tM, the thirdswitching device 218 continues to draw electric power and may sag thebus voltage 314 even further. In other words, the third switching device218 may utilize a lower bus voltage 314 than the first and secondswitching device 218.

Accordingly, in addition to adjusting the bus voltage, the pull-incurrent for each switching device 218 may be individually adjusted. Inother words, an optimal balance between the bus voltage 314 and thepull-in currents may be determined to improve detection of when each ofthe switching devices 218 makes. Additionally, when switching devices218 are closed sequentially, the timing of the make operation may beadjusted. For example, the third switching device 218 may be closed at alater time to enable the bus voltage 314 to recover as the power supply246 replenishes the DC bus 248. In other words, the bus voltage 314 usedto make the third switching device 218 may be controlled by adjustingwhen the third switching device 218 makes.

As described above, the temperature of the switching device 218 mayaffect the make time and/or break time of the switching device 218. Tohelp illustrate, FIG. 38 is a plot that depicts the make time 316 versustemperature 318. As depicted, the make time 316 of the switching device218 increases as the temperature 318 increases. In some embodiments, themake time may change by approximately 50 microseconds per degreeCelsius. The break time of the switching device 218 may similarly alsobe affected by temperature. Accordingly, the temperature of theswitching device 218 may be determined before each make operation andbreak operation to facilitate determining when to apply a currentprofile (e.g., make current or break current) that enables the switchingdevice 218 to make or break at a desired time.

Additionally, the plot depicts an impedance index 320 versus temperature222. More specifically, the impedance index 320 may represent theinverse of a measured impedance of the operating coil. Since theresistance of a conductor generally increases with temperature and theoperating coil 220 is simply a long conductive wire, the impedance ofthe operating coil 220 may also increase with temperature. Accordingly,as depicted the impedance index 320 (e.g., inverse of measuredimpedance) varies inversely with temperature.

As such, the impedance of the operating coil 220 may be utilized todetermine the temperature 318 of the switching device 218. For example,FIG. 39 depicts a process 322 for determining the temperature of theswitching device 218 during a make operation. The process 322 may beimplemented via computer-readable instructions stored in the tangiblenon-transitory memory 226, 20, 46 and/or other memories and executed viaprocessor 224, 19, 45 and/or other control circuitry. Generally, process322 includes applying the measurement current to the operating coil(process block 324), determining voltage across operating coil (processblock 326), determining impedance of the operating coil (process block328), and determining temperature of the switching device (process block330). Process 322 may be performed before each make operation tofacilitate determining the expected make time of the switching device218 based on temperature, as described above.

In some embodiments, the processor 224 may instruct the operating coildriver circuitry 222 to supply the measurement current to the operatingcoil 220 (process block 324). More specifically, the processor 224 mayoutput a reference voltage (e.g., Vref) that corresponds with themeasurement current. Based at least on the comparison of the nodevoltage and the reference voltage, the SR flip-flop 228 outputs a PWMsignal 268 that instructs the switch 232 to supply the measurementcurrent to the operating coil 220 by selectively connecting anddisconnecting electric power from the DC bus 248. Accordingly, theprocessor 224 may determine the operating coil voltage by multiplyingthe bus voltage 314 with the duty cycle of the PWM signal 268 (processblock 326).

Based on the operating coil voltage, the processor 224 may determine theimpedance of the operating coil 220 (process block 328). Morespecifically, since the operating coil voltage and the operating coilcurrent (e.g., measurement current) are known, the processor 224 maydetermine the operating coil impedance by dividing the operating coilvoltage by the measurement current and, thus, the impedance index 320.

Based on the operating coil impedance, the processor 224 may thendetermine the switching device temperature 318 (process block 330). Asdescribed above, the operating coil impedance directly relates to itstemperature 318. Accordingly, the processor 224 may determine thetemperature 318 based on that relationship. More specifically, in someembodiments, the relationship between temperature 318 and impedance maybe defined by a manufacturer. For example, the manufacture may define atemperature look-up-table (LUT) that takes the impedance index 320(e.g., inverse of operating coil impedance) input and outputs atemperature 318. Additionally or alternatively, in other embodiments, itmay be unnecessary to determine the exact temperature of the switchingdevice 218. Instead, it may be sufficient to use the operating coilimpedance 320 or the operating coil voltage with the operating coilcurrent as a proxy for temperature. In other words, the operating coilimpedance 320 or the operating coil voltage with the operating coilcurrent may be used as inputs to the make time LUT.

Furthermore, as described above, the break operation may also beaffected by the temperature of the switching device 218. Accordingly,FIG. 40 depicts one embodiment of a process 332 for determining thetemperature of the switching device 218 during a break operation. Theprocess 332 may be implemented via computer-readable instructions storedin the tangible non-transitory memory 226, 20, 46 and/or other memoriesand executed via processor 224, 19, 45 and/or other control circuitry.Generally, the process 332 includes applying the hold-in current to theoperating coil (process block 334), determining voltage across theoperating coil (process block 336), determining impedance of theoperating coil (process block 338), and determining temperature of theswitching device (process block 340). Process 332 may be performedbefore each break operation to facilitate determining the expected breaktime of the switching device 218 based on temperature, as describedabove.

In some embodiments, the processor 224 may instruct the operating coildriver circuitry 222 to supply the hold-in current to the operating coil220 (process block 334). More specifically, similar to process block324, the processor 224 may output a reference voltage (e.g., Vref) thatcorresponds with the hold-in current. Based at least on the comparisonof the node voltage and the reference voltage, the SR flip-flop 228outputs a PWM signal 268 that instructs the switch 232 to supply thehold-in current to the operating coil 220 by selectively connecting anddisconnecting electric power from the DC bus 248. Accordingly, similarto process block 326, the processor 224 may determine the operating coilvoltage by multiplying the bus voltage 314 with the duty cycle of thePWM signal 268 (process block 336).

Similar to process block 328, the processor 224 may determine theimpedance of the operating coil 220 based on the operating coil voltage(process block 338). More specifically, since the operating coil voltageand the operating coil current (e.g., hold-in current) are known, theprocessor 224 may determine the operating coil impedance by dividing theoperating coil voltage by the hold-in current and, thus, the impedanceindex 320.

Similar to process block 330, the processor 224 may then determine theswitching device temperature 318 based on the operating coil impedance(process block 340). As described above, the operating coil impedancedirectly relates to its temperature. Accordingly, the processor 224 maydetermine the temperature 318 based on that relationship, which may bedefined a manufacturer. Additionally or alternatively, in someembodiments, it may be sufficient to use the operating coil impedance orthe operating coil voltage with operating coil current as a proxy fortemperature. In other words, the impedance index 320 (e.g., inverse ofoperating coil impedance) or the operating coil voltage with theoperating coil current may be used as inputs to the break time LUT.

Accordingly, based on the techniques described above, the processor 224may use the PWM signal 268 to determine operational parameters of theswitching device 218, such as when the switching device 218 makes, whenthe switching device 218 breaks, and/or the temperature of the switchingdevice 218. Additionally, other diagnostic information may also bedetermined. For example, FIGS. 41A-C depict embodiments of determiningwellness of the switching device 218. More specifically, FIG. 41Adepicts one embodiment of a process 342 for determining wellness of theswitching device 218 with the measurement current, FIG. 41B depicts oneembodiment of a process 344 for determining wellness of the switchingdevice 218 during a make or break operation, and FIG. 41C depicts oneembodiment of a process 346 for determining wellness of the switchingdevice 218 with the hold-in current. The processes 342-346 may beimplemented via computer-readable instructions stored in the tangiblenon-transitory memory 226, 20, 46 and/or other memories executed viaprocessor 224, 19, 45 and/or other control circuitry.

As shown in FIG. 41A, process 342 generally includes applying themeasurement current to the operating coil (process block 348),monitoring the PWM signal (process block 350), and determining wellnessof the switching device (process block 352). More specifically, asdescribed above, the processor 224 may determine the switching devicetemperature 318 using the measurement current. Accordingly, theprocessor 224 may detect when excessive temperatures (e.g., out ofspecification) are present.

Additionally, in some embodiments, the processor 224 may detect whethera short circuit or an open circuit condition exits in the operating coil220. For example, if the PWM signal duty cycle jumps to 100%, theprocessor 224 may determine that an open circuit condition is present.On the other hand, if the PWM signal duty cycle is much lower thanexpected, the processor 224 may determine that a short circuit conditionis present. Furthermore, the measurement current may also monitortemperature changes in the switching device 218. For example, if the PWMsignal duty cycle begins to increase, the processor 224 may determinethat the temperature 318 is increasing. On the other hand, if the PWMsignal duty cycle begins to decrease, the processor 224 may determinethat the temperature is decreasing.

As shown in FIG. 41B, process 344 generally includes applying thepull-in or break current to the operating coil (process block 354),determining the make or break time of the switching device (processblock 356), and determining wellness of the switching device (processblock 358). More specifically, as described above, the processor 224 maydetermine the expected make time and/or break time of the switchingdevice 218. Additionally, the processor 224 may determine the actualmake time or break time. Accordingly, the processor 224 may detect whena faulty condition is present in the switching device 218. For example,if the determined make time is much shorter than expected, the processor224 may determine that the armature 118 is obstructed and not closingfrom a fully open position. On the other hand, if the determined maketime is much longer than expected, the processor 224 may determine thatthe armature 118 is obstructed from closing smoothly.

Additionally, the processor 224 may look at the trend of make times orbreak times. More specifically, the trend may indicate the gradual agingof the switching device 218. For example, the processor 224 may estimatethe age of the switching device (e.g., amount of life left) based on howmuch the make time or break time of the switching device 218 haschanged. Furthermore, as depicted in FIG. 38, the make time 316 trend isgenerally linear with regard to temperature 318. Accordingly, if therelationship begins to deviate from the expected or historical norm, theprocessor 224 may determine specific changes to the switching device218. For example, if the make time varies unpredictably, the processor224 may determine that environmental conditions, such as vibrations forsurround machinery, are affecting the make times.

As shown in FIG. 41C, process 346 generally includes applying thehold-in current to the operating coil (process block 360), monitoringthe PWM signal (process block 362), and determining wellness of theswitching device (process block 364). More specifically, as describedabove, the processor 224 may determine the switching device temperature318 using the hold-in current. Accordingly, the processor 224 may detectwhen excessive temperatures (e.g., out of specification) are present.Additionally, since the hold-in current may be applied to the operatingcoil 220 for an extended period of time, the processor 224 may alsomonitor temperature changes in the switching device 218. For example, ifthe PWM signal duty cycle begins to increase, the processor 224 maydetermine that the temperature 318 is increasing. On the other hand, ifthe PWM signal duty cycle begins to decrease, the processor 224 maydetermine that the temperature is decreasing. Furthermore, in someembodiments, if the PWM duty cycle is excessively varying, the processor224 may determine that the armature 118 is chattering (e.g., not still).

Since the hold-in current is generally applied to the operating coil 220for an extended period, the hold-in current may additionally be utilizedto monitor wellness of the system 10 that includes the switching device218. For example, one embodiment of a process 366 for monitoring thewellness of the system is shown in FIG. 41D. Generally, the process 366includes applying the hold-in current to the operating coil (processblock 368), monitoring the PWM signal (process block 370), andmonitoring wellness of the system (process block 372). In other words,the processor 224 may monitor the PWM signal 268 to monitor the wellnessof the system.

More specifically, electric power carried by the switching device 218generates a magnetic field, which may act on the operating coil 220. Forexample, in some embodiments, the magnetic field may induce a positivevoltage in the operating coil 220, which enables the voltage supplied bythe power source 246 to be reduced while still maintaining the hold-incurrent. As such, the PWM duty cycle may decrease. On the other hand,the magnetic field may induce a negative voltage in the operating coil220, which causes the power source 246 to supply larger amount ofvoltage to maintain the hold-in current. As such, the PWM duty cycle mayincrease.

Additionally, when the switching device 218 is closed, conductedelectric power may cause the stationary contactor assembly 124 to exerta force on the movable contactor assembly 116. In fact, under excessivecurrent, the stationary contact assembly 124 may exert sufficient forceon the movable contactor assembly 116 to cause armature 118 movement. Asdescribed above, movement may change impedance of the operating coil220. Accordingly, to maintain the operating coil current 250 at itstarget, the duty cycle of the PWM signal may adjust to compensate forthe change in impedance. In this manner, the PWM duty cycle mayfacilitate detecting excessive current conditions.

The PWM signal may also facilitate determining other characteristics ofthe source electric power and/or the load. For example, since theelectric power carried may be AC, the polarity and magnitude of thecurrent may continuously change. As such, since the magnitude andpolarity of the induced voltage depends on the magnitude and polarity ofcurrent being conducted, the processor 224 may determine the phase ofthe current being conducted by the switching device 218 based at leastin part on the changes in the PWM duty cycle. Thus, in some embodiments,since current will be largely cyclical, the processor 224 may determinewhen current zero-crossings will occur.

Based on the phase of the electric power, the processor 224 may alsodetermine the type of load the electric power is being supplied to.Generally, when electric power is supplied to an inductive load, thecurrent and the voltage will be out of phase. On the other hand, whenelectric power is supplied to a resistive load, the current and voltagewill be in phase. As such, the processor 224 may determine whether theelectric power is being supplied to an inductive load or a resistiveload by comparing the phase of the current to phase of the voltage, forexample, determined using sensors 22.

Phase Sequential Switching

As described above, one or more switching devices may be used to connector disconnect electric power from a load 18, such as an electric motor24. In some embodiments, to improve control over theconnection/disconnection of electric power, the switching devices may besingle pole switching devices, such as the single pole, single currentcarrying path switching devices 218. For example, three single poleswitching devices may be used in a direct on-line configuration witheach single pole switching device used to connect/disconnect one phaseof electric power. In fact, since they are single pole switchingdevices, the switching devices be independently controlled, therebyenabling various closing and/or opening sequences.

To help illustrate, a three phase direct on-line configuration isdescribed in 42A. As depicted, a first single pole switching device 335may control supply of a first phase (e.g., phase A) of electric powerfrom the power source 12 to the load 14, a second switching device 337may control supply of a second phase (e.g., phase B) of electric powerfrom the power source 12 to the load 14, and a third single poleswitching device 339 may control supply of a third phase (e.g., phase C)of electric power from the power source 12 to the load 14. As such, thesingle pole switching devices 335, 337, and 339 may be opened/closed invarious sequences.

For example, in some embodiments, the single pole switching devices 335,337, and 339 may be controlled to sequentially open/close. Oneembodiment of a process 341 for sequentially opening/closing the singlepole switching devices is described in 42B. Generally, the process 341includes opening/closing a first switching device (process block 343),opening/closing a second switching device (process block 345), andopening/closing a third switching device (process block 347). In someembodiments, process 341 may be implemented via computer-readableinstructions stored in a non-transitory article of manufacture (e.g.,the memory 226, 20, 46 and/or other memories) and executed via processor224, 19, 45 and/or other control circuitry.

Accordingly, at a first time, control circuitry 18 may instruct thefirst single pole switching device 335 to open or close (process block343). In this manner, the first phase of electric power may be connectedor disconnected at the first time. Additionally, at a second time, thecontrol circuitry 18 may instruct the second single pole switchingdevice 337 to open or close (process block 345). In this manner, thesecond phase of electric power may be connect or disconnected at thesecond time. Furthermore, at a third time, the control circuitry 18 mayinstruct the third single pole switching device 339 to open or close(process block 347). In this manner, the third phase of electric powermay be connected or disconnected at the third time. As such, the singlepole switching devices 335, 337, and 339 may be controlled tosequentially connect/disconnect each phase of electric power from thepower source 12 to the load 14.

In other embodiments, the single pole switching devices 335, 337, and339 may be controlled to open/close two and then open/close one oropen/close one and then open/close two. One embodiment of a process 349for opening/closing two and then opening/closing one is described in42C. Generally, the process 349 includes opening/closing a firstswitching device and a second switching device (process block 351) andopening/closing a third switching device (process block 343). In someembodiments, process 349 may be implemented via computer-readableinstructions stored in a non-transitory article of manufacture (e.g.,the memory 226, 20, 46 and/or other memories) and executed via processor224, 19, 45 and/or other control circuitry.

Accordingly, at a first time, control circuitry 18 may instruct thefirst single pole switching device 335 and the second single poleswitching device 337 to open or close (process block 351). In thismanner, the first phase and the second phase of electric power may beconnected or disconnected at the first time. Additionally, at a secondtime, the control circuitry 18 may instruct the third single poleswitching device 339 to open or close (process block 35.). In thismanner, the third phase of electric power may be connect or disconnectedat the second time. As such, the single pole switching devices 335, 337,and 339 may be controlled to connect/disconnect electric power from thepower source 12 to the load 14 by opening/closing two and then one.

In further embodiments, the single pole switching devices 335, 337, and339 may be controlled to open/close one and then open/close two. Oneembodiment of a process 355 for opening/closing one and thenopening/closing two is described in 42D. Generally, the process 355includes opening/closing a first switching device (process block 357)and opening/closing a second switching device and a third switchingdevice (process block 359). In some embodiments, process 355 may beimplemented via computer-readable instructions stored in anon-transitory article of manufacture (e.g., the memory 226, 20, 46and/or other memories) and executed via processor 224, 19, 45 and/orother control circuitry.

Accordingly, at a first time, control circuitry 18 may instruct thefirst single pole switching device 335 to open or close (process block357). In this manner, the first phase of electric power may be connectedor disconnected at the first time. Additionally, at a second time, thecontrol circuitry 18 may instruct the second single pole switchingdevice 339 and the third single pole switching device 339 to open orclose (process block 35). In this manner, the second phase and the thirdphase of electric power may be connect or disconnected at the secondtime. As such, the single pole switching devices 335, 337, and 339 maybe controlled to connect/disconnect electric power from the power source12 to the load 14 by opening/closing one and then two.

Moreover, since the single pole switching devices 335, 337, and 339 maybe independently controlled, this may enable adjusting the open/closesequence based on various desired. For example, this may be particularlyuseful to implement point-on-wave (POW) techniques. More specifically,when connecting electric power, control circuitry 18 may utilize a closetwo then one sequence, thereby reducing magnitude of in-rush currentand/or current oscillations. On the other hand, when disconnectingelectric power, the control circuitry 18 may utilize an open one thentwo sequence, thereby reducing likelihood and/or magnitude of arcing.

In addition to connecting/disconnecting electric power direct on-line,the one or more switching devices (e.g., single-pole, singlecurrent-carrying path switching devices) may be used in a wye-deltastarter, which provides electric power to the electric motor 24.Generally, the wye-delta starter may start the electric motors 24 byconnecting the windings in a wye (e.g., star) configuration in order tolimit the amount of voltage supplied to the windings, thereby limitingin rush current to the motor 24 and/or torque produced by the motor 24.Subsequently, the wye-delta starter may connect the windings in theelectric motor 24 in a delta configuration after the motor 24 is startedto increase the voltage supplied to the windings, thereby increasing thetorque produced by the motor. In other words, a wye-delta starter mayease starting of the electric motor 24 by gradually increasing suppliedelectric power, thereby gradually increasing produced torque.

In some instances, opening and closing the switching devices totransition the electric motor 24 between the various configurations maydischarge electric power (e.g., arcing), cause negative torque in theelectric motor 24, cause current spikes that could trip upstreamdevices, cause current oscillations, or the like. As can be appreciated,such events may reduce the lifespan of the switching devices, theelectric motor 24, the load, and/or other connected equipment.

As such, it would be beneficial to reduce likelihood and/or magnitude ofsuch events when transitioning between the various configurations. Aswill be described in more detail below, one embodiment described hereinmay reduce these effects by transition between the wye configuration andthe delta configuration using single-pole switching devices, such as thesingle pole, single current path switching devices 218 described above.More specifically, using single-pole switching devices may enablerelatively independently controlling opening and/or closing, forexample, in a sequential manner. In other words, each of the windings ofthe motor 24 may not simultaneously transition from a wye configurationto delta configuration or vice versa.

To help illustrate, a process for sequential starting of a motor 24using a 5-pole wye-delta starter 374 is described in reference to FIGS.43A-H. To simplify the following discussion, the wye-delta starter 374is described as using five single pole switching devices, such as thesingle-pole, single current-carrying path switching devices 218described above. However, any other suitable switching device mayadditionally or alternatively be used in the techniques describedherein. For example, in some embodiments, a multi pole, multi-currentcarrying path switching device (e.g., three-pole contactor) with off-setpoles may be used.

It should be further noted that point-on-wave (POW) techniques may ormay not be utilized in the embodiments described below. As describedabove, when POW techniques are utilized, sensors 22 may monitor (e.g.,measure) the characteristics (e.g., voltage or current) of the electricpower supplied to the electric motor 24. The characteristics may becommunicated to the control and monitoring circuitry 18 to enabledetermining the timing for making and/or breaking the switching devicesat a specific point on the electric power waveform.

More specifically, when POW techniques are utilized, a reference pointmay be selected on a waveform and the timings for energizing the coilsand opening/closing switching devices may be calculated. Commands may besent to timers and the like based on the calculated timings. Once thereference point is hit, the sequence may begin and the timers maytrigger the switching devices to open or close when the calculated timesare encountered (e.g., after a configurable amount of electrical degreesand/or based a predicted current zero-crossing). In this manner, whenPOW techniques are utilized, the wye-delta starter 374 may progressthrough each step in a two-step start and a wye-delta phase sequentialtransition based at least in part on current zero-crossings and/orpredicted current zero-crossing. On the other hand, when POW techniquesare not utilized, the wye-delta starter 374 may progress through eachstep in the two-step start and the wye-delta phase sequential transitionone at a time, for example, after a brief time delay (e.g.,milliseconds).

In some embodiments, continuous current flow may be provided to themotor 24 during the transition from wye to delta (e.g., “closedtransition”) by supplying current to at least one winding during thetransition. More specifically, supplying current to at least one windingmay facilitate maintaining a relationship between the rotor field andthe line electric power. In this manner, when subsequent windings areconnect to the line electric power, in rush current may be reduced,which may obviate transition resistors.

As depicted, the 5-pole wye-delta starter 374 includes five switchingdevices 376, 378, 380, 382, and 384 used to selectively connect threemotor windings 386, 388, and 390 to a three-phase power source (e.g.,mains lines 392, 394, and 396 each carrying a single phase of power). Insome embodiments, the first wye switching device 376 and the second wyeswitching device 378 may have the same operational characteristics.Additionally, the first delta switching device 380, the second deltaswitching device 382, and the third delta switching device 384 may havethe same operational characteristics. For example, in some embodiments,the delta switching device 380, 382, and 384 may be single-pole, singlecurrent carrying path switching devices 218 and the wye switchingdevices 376 and 378 may be power electronic switching devices, such assilicon-controlled rectifiers (SCRs), insulated-gate bipolar transistors(IGBTs), or power field-effect transistors (FETs), or otherbidirectional devices.

In the depicted embodiment, dashed lines are used to indicatenon-conducting pathways and solid lines are used to indicate conductingpathways. As such, FIG. 43A describes when each of the switching devices376, 378, 380, 382, and 384 is open, thereby disconnecting the electricpower from the windings 386, 388, and 390. The wye-delta starter 374 maythen transition to a wye configuration using a two-step start sequence,as described in FIGS. 43B and 43C. From the wye configuration, thewye-delta starter 374 may then transition to a delta configuration usingphase sequential switching, as described in FIGS. 43D-H.

As described above, FIGS. 43B and 43C describe transitioning theelectric motor 24 to a wye configuration using a two-step process. Morespecifically, as shown in FIG. 43B, the second wye switching device 378may be closed to provide power to the motor windings 388 and 390. Insome embodiments, the second wye switching device 378 may be closedbased at least in part on a predicted current zero-crossing to reducemagnitude of in rush current and current oscillations. Additionally, asshown in FIG. 43B, the first wye switching device 376 may be closed toprovide three-phase power to the motor windings 386, 388, and 390. Insome embodiments, the first wye switching device 376 may be closed aftera delay to reduce magnitude of current and/or torque oscillations, forexample, based on a predicted current zero-crossing. In this manner, thewye-delta starter may run the electric motor 24 in the wyeconfiguration.

After the electric motor 24 is running in the wye configuration, currentflowing through windings 386, 388, and 390 may be balanced. As describedabove, the electric motor 24 may be started in the wye configuration sothat the electric motor 24 produces a reduced amount of torque andconsumes less power. In other words, as will be described in more detailbelow, starting in the wye configuration enables the electric motor 24to be gradually started.

The wye-delta starter 374 may then transition to running the electricmotor 24 in a delta configuration to increase torque output (e.g., rampup the motor 24). In some embodiments, the transition to the deltaconfiguration may initiate after connecting in the wye configuration,for example, to enable the electric motor 24 to reach steady stateand/or reduce magnitude of torque adjustments.

More specifically, the wye-delta starter 374 may begin transition fromthe wye configuration to the delta configuration by opening the firstwye switching device 376, as shown in FIG. 43D. As a result, electricpower is only supplied to motor windings 388 and 390, which stops thestator field. More specifically, as shown in FIG. 43E, the first deltaswitching device 380 may be closed, thereby connecting first winding 386in the delta configuration (e.g., line 392 to line 394) while windings388 and 390 remain connect in the wye configuration. As a result, thestator field may be reintroduced, thereby producing a positive torque.In fact, in some embodiments, the closure of first delta switchingdevice 380 may be delayed to enable any arcing produced from the openingfirst wye switching device 376 to dissipate and/or mute adjustmentbetween the stator field and the rotor field, for example, to reducemagnitude of current and/or torque oscillations.

Additionally, as depicted in FIG. 43F, the second wye switching device378 may be opened such that only the first winding 386 continues toreceive power. In some embodiments, the opening of the second wyeswitching device 378 may occur based on (e.g., at or ahead of) a currentzero-crossing in order to reduce likelihood and/or magnitude of arcing.

Furthermore, the second delta switching device 382 may be closed afterthe opening of the second wye switching device 378, thereby providingpower to second winding 388 as depicted in FIG. 43G. More specifically,when the second wye switching device 378 is open, the stator field stopsrotating and while the speed strength of the rotor field graduallydiminishes. Thus, waiting too long to close second delta switchingdevice 382 may increase inrush current and/or cause the rotor field topass the stator field, thereby producing a whipsaw effect of brakingtorque as the stator and rotor fields try to sync.

Accordingly, in some embodiments, the closure timing of second deltaswitching device 382 may be a short delay (e.g., a few milliseconds or aconfigurable number of electrical degrees) after second wye switchingdevice 378 opens to reduce the likelihood of the rotor field passing thestator field. For example, the second delta switching device 382 mayclose based upon where a predicted current zero-crossing. Additionally,the closure timing of second delta switching device 382 may enable anyarcing resulting from the opening of second wye switching device 378 tobe extinguished before closing. For example, in some embodiments, seconddelta switching device 382 may be closed two hundred forty electricaldegrees after the first delta switching device 380 closure.

As depicted in FIG. 43H, the third delta switching device 384 may beclosed. In some embodiments, the third delta switching device 384 mayclose based upon a predicted current-zero crossing. Once the third deltaswitching device 384 is closed, three-phase power is supplied to thethree motor windings 386, 388, and 390 via the closed switching devices380, 382, and 384 in the delta configuration. As such, the motor 24 mayaccelerate to full torque capabilities in the delta configuration.

Although each switching device 376, 378, 380, 382, and 384 is describedas sequentially opening or closing, in other embodiments one or more ofthe switching devices may open or close substantially simultaneous. Forexample, in some embodiments, switching devices 382 and 384 may beclosed substantially simultaneously. In this manner, an interim torquelevels may be removed and the motor may accelerate to full load faster.

One embodiment of a process 398 for controlling the wye-delta starter374 to transition an electric motor 24 from an open configuration to awye configuration and to a delta configuration is described in FIG. 44A.Generally, the process 398 includes closing a second wye switchingdevice 378 (process block 399) and closing a first wye switching device376 after closing first wye switching device 376 (process block 400) torun the electric motor 24 in the wye configuration. Additionally, theprocess 398 includes opening the first wye switching device 376 (processblock 401), closing a first delta switching device 380 after the firstwye switching device 376 opens (process block 402), opening the secondwye switching device 378 (process block 404), closing a second deltaswitching device 382 after the first delta switching device 380 closes(process block 406), and closing a third delta switching device 384after the first delta switching device 380 closes (process block 408) torun the electric motor 24 in the delta configuration. In someembodiments, process 398 may be implemented via computer-readableinstructions stored in a non-transitory article of manufacture (e.g.,the memory 226, 20, 46 and/or other memories) and executed via processor224, 19, 45 and/or other control circuitry.

In some embodiments, process 398 may begin when the wye-delta starter374 is in the open configuration, thereby disconnecting electrical powerfrom the electric motor 24 (e.g., FIG. 43A). To connect the electricmotor 24 in the wye-configuration, control circuitry 18 may instruct thesecond wye switching device 378 to close (process block 399) and thefirst wye switching device 376 to close after closure of the second wyeswitching device 378 (process block 400). In some embodiments, thecontrol circuitry 18 may instruct the wye switching devices 376 and 378to close based at least in part on a predicted current zero-crossingand/or at a configurable number of electrical degrees apart from eachother. For example, the control circuitry 18 may instruct second wyeswitching device 378 to close at a line-to-line voltage maximum (e.g., apredicted current zero-crossing) and the first wye switching device 376to close sixty electrical degrees later (e.g., a predicted currentzero-crossing), thereby reducing magnitude of in-rush current and/orcurrent oscillations.

From the wye configuration, control circuitry 18 may instruct the firstwye switching device 376 to open (process block 401). In someembodiments, the control circuitry 18 may instruct the first wyeswitching device 376 to open based at least in part on a currentzero-crossing (e.g. at or before a current zero-crossing), which mayreduce arcing and extend the life of the first wye switching device 376,the electric motor 24, the load, and/or other connected electricalcomponents.

After first wye switching device 376 is opened, control circuitry 18 mayinstruct the first delta switching device 380 to close (process block402). In some embodiments, the control circuitry 18 may instruct thefirst delta switching device 380 to close based at least in part on apredicted current zero-crossing and/or at a configurable number ofelectrical degrees after the first switching device 376 opens. Forexample, in some embodiments, the control circuitry 18 may instructfirst delta switching device 380 to close thirty electrical degrees(e.g., a predicted current zero-crossing) after first wye switchingdevice 376 is opened.

Control circuitry 18 may then instruct second wye switching device 378to open (process block 404). In some embodiments, the control circuitry18 may instruct second wye switching device 378 to open based at leastin part on a next subsequent current zero-crossing, thereby reducinglikelihood and/or magnitude of arcing and current spikes.

Additionally, after first delta switching device 380 is closed, thecontrol circuitry 18 may instruct second delta switching device 382 toclose (process block 406) and third delta switching device 384 to close(process block 408). In some embodiments, the control circuitry 18 mayinstruct second delta switching device 382 and third delta switchingdevice 384 to close based at least in part on a predicted currentzero-crossing and/or at a configurable number of electrical degreesafter the first wye switching device 376 opened. For example, thecontrol circuitry 18 may instruct second delta switching device 382 toclose a two hundred forty electrical degrees (e.g., a predicted currentzero-crossing) after the first delta switching device 380 closure andinstruct third delta switching device 384 to close four hundred twentyelectrical degrees (e.g., a predicted current zero-crossing) after thefirst delta switching device 380 closure.

In some embodiments, it may be desirable to close the second deltaswitching device 382 quickly because the stator field may stall afterthe second wye switching device 378 opens. As such, waiting an extendedperiod before closing second delta switching device 382 may result inthe rotor field to passing the stator field, which may lead to torqueoscillations (e.g., a whipsaw effect) as the fields try to sync and/orcurrent spikes in the motor 24.

In this manner, the control circuitry 18 may instruct the wye-deltastarter 374 to gradually transition an electric motor 24 from the openconfiguration to the wye-configuration and to the delta-configuration.In other words, the wye-delta starter 374 may be controlled to graduallyadjust speed and/or or torque of the motor 24 by sequentiallyopening/closing the switching devices 376-384.

Additionally, it should be noted that the described electrical degreesare merely intended to be illustrative. In fact, in some embodiments,the number of electrical degrees may be dynamically adjusted by thecontrol circuitry 18 and/or firmware of the switching devices based atleast in part on supplied electrical power, application (e.g., load),environmental factors (e.g., dust, condition of switching devices and/orload, etc.), and so forth. For example, as described above, the timingof opening/closing a switching device may be adjusted to reducelikelihood of arcing, magnitude of arcing, magnitude of currentoscillations, magnitude of torque oscillations, magnitude of in-rushcurrent, likelihood of current spikes, magnitude of current spikes, orany combination thereof. Additionally, in some embodiments, the timingsmay be adjusted based at least in part on the type of application theelectric motor 24 is used in. For example, when driving a chiller, longdelays may not be acceptable because and, thus, the adjusted to beshorter. Further, the timings may be adjusted based at least in part onthe power factor of the AC electric power system.

To facilitate, the timings may be adjusted by multiples of thirtyelectrical degrees (e.g., thirty, sixty, ninety, etc.), multiples of onehundred eighty electrical degrees (e.g., one hundred eighty, threehundred sixty), multiples of three hundred sixty degrees, multiples ofseven hundred twenty degrees, or so forth. In fact, delaying the timingsmay enable electric power to stabilize, thereby reducing magnitude ofcurrent oscillations and/or current spikes. More specifically, a lowermagnitude of current oscillation and/or current spikes may improveadjustments between the stator field and the rotor field. As such, insome embodiments, the timing of each subsequent opening/closing may bebased at least in part on when electric power supplied to the windings386, 388, and 390 stabilize.

To help illustrate, a plot 409 of magnitude of current supplied to theelectric motor 24 is described in FIG. 44B. More specifically, the plot409 includes a current curve 411 that describes magnitude of currentsupplied to windings 386, 388, and 390 in the electric motor between t0when motor 24 is connect in an open configuration (e.g., FIG. 43A) to t7when the motor 24 is connected in a delta configuration (e.g., FIG.43H).

As described by the current curve 411, the magnitude of current suppliedto the electric motor 24 is zero between t0 and t1. Thus, between t0 andt1, the wye-delta starter 374 may be in the configuration described inFIG. 43A, thereby disconnecting electric power from the windings 386,388, and 390. Additionally, the magnitude of current supplied to theelectric motor 24 increases at t1 and reaches a steady state before t2.Thus, between t1 and t2, the wye-delta starter 374 may be in theconfiguration described in FIG. 43B, thereby connecting electric powerto windings 388 and 390 in the wye configuration. Furthermore, themagnitude of current supplied to the electric motor 24 again increasesat t2 and reach a steady state before t3. Thus, between t2 and t3, thewye-delta starter 374 may be in the configuration described in FIG. 43C,thereby connecting electric power to each of the windings 386, 388, and390 in the wye configuration.

As described by the current curve 411, the magnitude of the currentsupplied to the electric motor 24 may decrease at t3 and reach a steadystate before t4. Thus, between t3 and t4, the wye-delta starter 374 maybe in the configuration described in FIG. 43D, thereby connectingelectric power to windings 388 and 390 in the wye configuration.Additionally, the magnitude of the current supplied to the electricmotor 24 may increase at t4 and reach a steady state before t5. Thus,between t4 and t5, the wye-delta starter 374 may be in the configurationdescribed in FIG. 43E, thereby connecting electric power to windings 388and 390 in the wye configuration and first winding 386 in the deltaconfiguration.

Furthermore, the magnitude of current supplied to the electric motor 24may be again increased at t5 and reach a steady state before t6. In someembodiments, between t5 and t6, the wye-delta starter 374 may operatesuch that, at a first time, the second winding 388 is connected in thewye configuration, first winding 386 is connected in a deltaconfiguration, and third winding 390 is connected in both the wye andthe delta configuration and, at a second time, the second winding 388remains connected in the wye configuration and windings 386 and 388 areconnected in the delta configuration. In other embodiments, between t5and t6, the wye delta starter 384 may operate such that, at a firsttime, the first winding 386 is connected in the delta configuration(e.g., FIG. 43F) and, at a second time, windings 386 and 388 areconnected in the delta configuration (e.g., FIG. 43G).

As described by the current curve 411, the magnitude of the currentsupplied to the electric motor 24 may increase at t6 and reach a steadystate before t7. Thus, between t6 and t7, the wye-delta starter 374 maybe in the configuration described in FIG. 43H, thereby connectingelectric power to windings 386, 388 and 390 in the delta configuration.Thus, in the described embodiment, the timing of opening/closing of theswitching devices 376-384 may be determined such that subsequentopening/closing is performed after the electric motor 24 stabilizes(e.g., magnitude of current reaches a steady state), thereby reducingmagnitude of current spikes, current oscillations, and/or torqueoscillations produced by sequential switching.

Moreover, in some embodiments, POW techniques may also be utilized toimprove sequential switching of the wye-delta starter 374. As describedabove, when POW techniques are utilized, the wye-delta starter 374 mayprogress through each step in the sequential switching based at least inpat on current zero-crossings and/or predicted current zero-crossings.To help illustrate, current and voltage waveforms of the power source 12and the windings 386, 388, and 390 are described.

Since connecting the windings 386, 388, and 390 in a wye configurationis essentially connecting three phase electric power, the current andvoltage waveforms describing transitioning from disconnected to the wyeconfiguration are described in relation to FIGS. 5A-5C between t0 andt2. In this context, FIG. 5A illustrates the voltage of three-phaseelectric power (e.g., a first phase voltage curve 66, a second phasevoltage curve 68, and a third phase voltage curve 70) provided by apower source 12. FIG. 5B illustrates the line to neutral voltagesupplied to each terminal (e.g., first terminal voltage curve 72, secondterminal voltage curve 74, and third terminal voltage curve 76) of theelectric motor 24. FIG. 5C illustrates line current supplied to eachwinding (e.g., first winding current curve 77, second winding currentcurve 78, and third winding current curve 80) of the electric motor 24.

As described above, between t0 and t1, the switching devices 376-384 areopen and electric power is not connected to the electric motor 24. Att1, the second wye switching device 378 is closed to connect a firstphase (e.g., phase A) and a second phase (e.g., phase B) of the electricpower to the second winding 388 and the third winding 390 in the wyeconfiguration. To reduce magnitude of in-rush current and/or currentoscillations, the wye-delta starter 374 may close the second wyeswitching device 278 based at least in part on a predicted currentzero-crossing (e.g., within a range from slightly before to slightlyafter the predicted current zero-crossing).

As described above, a predicted current zero-crossing may correspondwith a line-to-line voltage maximum (e.g., 90° after a voltagezero-crossing). With regard to FIG. 5A, the predicted currentzero-crossing occurs approximately when the line-to-line voltage betweenthe second phase (e.g., second phase voltage curve 68) and the thirdphase (e.g., third phase voltage curve 70) is at a maximum. Accordingly,by closing the second wye switching device 278 at t1, electric power isconnected to the second winding 388 and the third winding 390 atapproximately the predicted current zero-crossing. In fact, as depictedin FIG. 5C, since electric power is connected based at least in part ona predicted current zero-crossing, the current supplied to the secondwinding 388 (e.g., second winding current curve 79) and the thirdwinding 390 (e.g., second winding current curve 80) start at zero andgradually change, thereby reducing magnitude of in-rush current and/orcurrent oscillation.

After second wye switching device 378 is closed, first wye switchingdevice 376 is closed at t2 to supply the third phase (e.g., phase C) ofthe electric power to the first winding 386 in the wye configuration. Toreduce magnitude of in-rush current and/or current oscillations, thewye-delta starter 374 may connect electric power to the first winding386 based at least in part on a predicted current zero-crossing. Withregard to FIG. 5A, the predicted current zero-crossing occurs when thesum of line-to-line voltage between the first phase (e.g., first phasevoltage curve 66) and the third phase (e.g., third phase voltage curve70) and the line-to-line voltage between the first phase (e.g., secondphase voltage curve 66) and the second phase (e.g., third phase voltagecurve 68) is at a maximum. Accordingly, by closing the first wyeswitching device 376 at t2, electric power is connected to the firstwinding 386 at approximately the predicted current zero-crossing. Infact, as depicted in FIG. 5C, since the electric power connected basedat least in part on a predicted current zero-crossing, the currentsupplied to the first winding 386 (e.g., first winding current curve 78)starts at zero and gradually change, thereby rotating the electric motor24 and reducing magnitude of in-rush current and/or current oscillation.

To further illustrate, FIGS. 45A-C depicts current and voltage waveformsfor transitioning from the wye configuration to the delta configuration.Specifically, FIG. 45A illustrates the line to neutral voltage suppliedto each terminal (first terminal voltage curve 414, second terminalvoltage curve 412, and third terminal voltage curve 416) of the electricmotor 24. Additionally, 45B illustrates the voltage of three-phaseelectric power (e.g., a first phase voltage curve 420, a second phasevoltage curve 418, and a third phase voltage curve 422) provided by apower source 12. FIG. 45C illustrates line current supplied to eachwinding (e.g., first winding current curve 422, second winding currentcurve 424, and third winding current curve 426) of the electric motor24.

As described above, the first wye switching device 376 is opened at t3to disconnect electric power from the first winding 386. To reduce thelikelihood and/or magnitude of arcing, the wye-delta starter 374 mayopen the first wye switching device 376 based at least in part of acurrent zero-crossing (e.g., at or slightly before the currentzero-crossing). With regard to FIG. 45C, the current zero-crossingoccurs when current supplied to the first winding 386 (e.g., firstwinding current curve 422) is zero. Accordingly, by opening the firstwye switching device 376 at t3, electric power is disconnected from thefirst winding 386 at approximately the current zero-crossing.

After the first wye switching device 376 is opened, first deltaswitching device 380 may be closed at t4 to connect electric power tothe first winding 386 in the delta configuration. To reduce magnitude ofin-rush current and/or current oscillations, the wye-delta starter 374may close the first delta switching device 380 based at least in part ona predicted current zero-crossing (e.g., within a range from slightlybefore to slightly after the predicted current zero-crossing). Withregard to FIG. 45B, the predicted current zero-crossing occurs halfwaybetween t3 and t4 when the sum of line-to-line voltage between the firstphase (e.g., first phase voltage curve 420) and the third phase (e.g.,third phase voltage curve 416) and the line-to-line voltage between thefirst phase (e.g., second phase voltage curve 420) and the second phase(e.g., second phase voltage curve 418) is at a maximum. Accordingly, byclosing the first wye switching device 376 at t4, the first wyeswitching device 376 is closed slightly after the predicted currentzero-crossing. Nevertheless, as depicted in FIG. 45C, since electricpower is connected based at least in part on the predicted currentzero-crossing, the current supplied to the first winding 386 (e.g.,first winding current 422) starts at zero and gradually changes, therebyreducing magnitude of in-rush current and/or current oscillation.

Furthermore, at t4, the electric motor windings 386-390 are connected ina mixed wye-delta configuration. Accordingly, as depicted in FIG. 45C,the current supplied to the windings (e.g., first winding current curve422, second winding current curve 424, and third winding current curve426) is unbalanced, which may cause the winding (e.g., 388 and 390)connected in wye and the winding (e.g., 386) connected in delta toproduce varying magnetic fields. In other words, the electric motor 24may be unbalanced while still producing a positive torque.

After first delta switching device 380 is closed, second wye switchingdevice 378 may be opened and second delta switching device 382 may beclosed at t5 to connect the second winding 388 in the deltaconfiguration. To reduce the likelihood and/or magnitude of arcing, thewye-delta starter 374 may open the second wye switching device 378 basedat least in part of a current zero-crossing. With regard to FIG. 45C,the current zero crossing occurs when current supplied to the secondwinding 388 (e.g., second winding current curve 424) and the thirdwinding 390 (e.g., third winding current curve 426) are zero.Accordingly, by opening the second wye switching device 378 at t5, thesecond and third windings 388 and 390 are disconnected approximately atthe current zero-crossing.

Additionally, to reduce magnitude of in-rush current and/or currentoscillations, the wye-delta starter 374 may close the second deltaswitching device 382 based at least in part on a predicted currentzero-crossing. With regard to FIG. 45B, the predicted currentzero-crossing occurs at a line-to-line voltage maximum between the firstphase (e.g., first phase voltage curve 420) and the second phase (e.g.,second phase voltage curve 418). Accordingly, by closing the seconddelta switching device 382 at approximately t5, electric power isconnect to the second winding 388 at approximately the predicted currentzero-crossing. In fact, as depicted in FIG. 45C, since electric power isconnected based at least in part on the predicted current zero-crossing,the current supplied to the second winding 388 (e.g., second windingcurrent 424) starts at zero and gradually changes, thereby reducingmagnitude of in-rush current and/or current oscillation.

After first delta switching device 380 is closed, the third deltaswitching device 384 is may be close at t6. To reduce magnitude ofin-rush current and/or current oscillations, the wye-delta starter 374may close the third delta switching device 384 based at least in part ona predicted current zero-crossing. With regard to FIG. 45B, thepredicted current zero-crossing occurs when the sum of line-to-linevoltage between the first phase (e.g., first phase voltage curve 420)and the third phase (e.g., third phase voltage curve 416) and theline-to-line voltage between the third phase (e.g., third phase voltagecurve 416) and the second phase (e.g., second phase voltage curve 418)is at a maximum. Accordingly, by closing the third delta switchingdevice 384 at t6, electric power is connect to the third winding 390 atapproximately the predicted current zero-crossing. In fact, as depictedin FIG. 45C, since electric power is connected based at least in part onthe predicted current zero-crossing, the current supplied to the thirdwinding 390 (e.g., third winding current 426) starts at zero andgradually changes, thereby reducing magnitude of in-rush current and/orcurrent oscillation.

Thus, in the described embodiment, the timing of opening/closing of theswitching devices 376-384 may be determined such based at least in parton current zero-crossings and/or predicted current zero-crossings. Asdiscussed above, this may facilitate reducing in-rush current and/orcurrent oscillations when a switching device is closed and reducelikelihood and/or magnitude of arcing when a switching device is open.In this manner, the wye-delta starter 374 may utilize sequentialswitching to gradually adjust speed and/or torque of the electric motor24, particularly during startup.

In fact, the timing of the sequential switching may also be determinedbased on a balance between desired ramp up duration, strain on the motor24, and/or strain on the load 14. For example, in some embodiments, toreduce ramp up duration, the wye-delta starter 374 may adjustconfiguration of the first wye switching device 376-382 as soon asmagnitude of the supplied current stabilizes. Additionally, to reducestrain on the motor 24, the wye-delta starter 374 may remain at eachconfiguration a differing duration. For example, duration that theelectric motor 24 is run a wye configuration (e.g., between t2 and t3)may be longer than duration that the electric motor 24 is run in a mixedwye-delta configuration (e.g., between t3 and t4). In some embodiments,duration that the electric motor 24 is run in a first mixed wye-deltaconfiguration (e.g., between t4 and t5) may be longer than duration thatthe electric motor 24 is run in a second mixed wye-delta configuration(e.g., between t3 and t4).

Once in the delta configuration, the wye-delta starter 374 may enablethe electric motor 24 to utilize maximum (e.g., 100%) torque and/ormaximum (e.g., 100%) speed capabilities. In other words, the torqueand/or speed capabilities of the electric motor 24 may be increased whenrunning in the delta configuration as compared to running in the wyeconfiguration. However, power consumption by the electric motor 24 mayalso be increased. As such, in certain scenarios, it may be beneficialfor the wye-delta starter 374 to transition the motor 24 from the deltaconfiguration back to the wye configuration, thereby reducing powerconsumption.

One embodiment of a process 428 that describes the transition betweenwye to delta and vice versa is shown in FIG. 46. Generally, the process428 includes the same steps 401-408 shown in FIG. 44A to phasesequentially switch from wye to delta. To transition from delta to wye,the process 428 includes opening the third delta switching device 384(process block 430), opening the second delta switching device 382(process block 432), closing the second wye switching device 378 afterthe second delta switching device 382 opens (process block 434), openingthe first delta switching device 380 (process block 436), and closingthe first wye switching device 376 after the second wye switching device378 closes (process block 438). In some embodiments, the process 428 maybe implemented via computer-readable instructions stored in a tangiblenon-transitory article of manufacture (e.g., the memory 226, 20, 46and/or other memories) and executed via processor 224, 19, 45 and/orother control circuitry.

As previously noted, when POW techniques are not utilized the wye-deltastarter may progress through each step in the sequential switching aftera brief time delay (e.g., milliseconds) or substantially simultaneously.On the other hand, when POW techniques are utilized the wye-deltastarter may progress through each step in the wye two-step start andphase sequential wye-delta switching after a configurable number ofelectrical degrees and/or based at least in part on currentzero-crossings.

Turning now to the process 428, the phase sequential wye-delta switchingprocess blocks (process blocks 401, 402, 404, 406, and 408) describedabove with reference to FIG. 44A are reproduced in order to aid inunderstanding how the techniques enable sequentially switching back andforth between wye and delta as desired. As such, the detaileddescription of each process block in the phase sequential wye-deltaswitching in FIG. 44A is incorporated here by reference.

Thus, at process block 408, the electric motor 24 is running in a deltaconfiguration. From the delta configuration, control circuitry 18 mayinstruct third delta switching device 384 to open (process block 430)and instruct second delta switching device 382 to open (process block432). In some embodiments, the control circuitry 18 may instruct thirddelta switching device 384 and second delta switching device 382 to openbased at least in part on current zero-crossings (e.g., slightly beforeor at the current zero-crossings) to reduce likelihood and/or magnitudeof arcing. Additionally or alternatively, the control circuitry 18 mayinstruct the third delta switching device 384 to open at any time whilethe electric motor 24 is running in the delta configuration. Forexample, in some embodiments, third delta switching device 384 may beopened first and second delta switching device 382 opened subsequently.In other embodiments, both of the switching devices 382 and 384 may beopened simultaneously. After both the switching devices 382 and 384 areopened, the electric power is only connect to the first winding 386connected in the delta configuration.

After switching devices 382 and 384 are opened, the control circuitry 18may instruct the second wye switching device 378 to close (process block434). In some embodiments, the control circuitry 18 may instruct secondwye switching device 378 to based at least in part on a predictedcurrent zero-crossing after the wye switching devices are opened. Oncesecond wye switching device 378 is closed, the motor may be running in amixed wye-delta configuration with first winding 386 in connected in thedelta configuration and windings 388 and 390 connected in the wyeconfiguration. As a result, as discussed above, the winding currents maybe unbalanced.

Then, control circuitry 18 may instruct the first delta switching device380 to open (process block 436). In some embodiments, the controlcircuitry 18 may instruct first delta switching device 380 to open basedat least in part on a current zero-crossing (e.g., slightly before or atthe current zero-crossing) to reduce magnitude and/or likelihood ofarcing. Opening the first delta switching device 380 may remove powerfrom the first winding 386. As such, at this point, windings 388 and 390may be supplied power in the wye configuration.

Additionally, after first delta switching device 378 is opened, controlcircuitry 18 may instruct first wye switching device 376 to close(process block 438). In some embodiments, the control circuitry 18 mayinstruct first wye switching device 376 to close based at least in parton a predicted current zero-crossing. Once the first wye switchingdevice 376 closes, the electric motor 24 may be running in the wyeconfiguration. As a result, the current in windings 386, 388, and 390may be balanced and the amount of power consumed and torque produced maybe reduced.

It should be noted that once the electric motor 24 is running in the wyeconfiguration, the process 428 enables phase sequentially switching backto delta configuration by returning to process block 401. In thismanner, the wye-delta starter 374 may transition running the electricmotor 24 in either configuration (e.g., wye or delta) as desired(represented by arrows 440).

In the above described embodiments, the five switching device areutilized in the wye-delta starter 374. As such, the above wye-deltastarter 374 may be referred to herein as a 5-pole wye-delta starter.However, in other embodiments, it may be possible to increase amount ofcontrol over electric power supplied to the electric motor 24 byincreasing number of switching devices utilized in the wye-deltastarter. For example, in some embodiments, six switching devices may beutilized. Thus, such a wye-delta starter may be referred to herein as a6-pole wye-delta starter. As will be described in more detail below, a6-pole wye-delta starter may further extend the life span of theswitching devices by enabling the switching devices to take turns whenswitching.

To help illustrate, a 6-pole wye-delta starter 442 is described in FIGS.47A-G. To simplify the following discussion, the wye-delta starter 442is described as using single pole switching devices, such as thesingle-pole, single current-carrying path switching devices 218described above. However, any other suitable switching device mayadditionally or alternatively be used in the techniques describedherein. For example, in some embodiments, a multi-pole, multi-currentcarrying path switching device (e.g., three-pole contactor) with off-setpoles may be used.

As with the 5-pole wye-delta starter 374, is defined by the circuitdiagrams 442 FIGS. 47A-G. It should be further noted that point-on-wave(POW) techniques may or may not be utilized in the embodiments describedbelow. As described above, when POW techniques are utilized, sensors 22may monitor (e.g., measure) the characteristics (e.g., voltage orcurrent) of the electric power supplied to the electric motor 24. Thecharacteristics may be communicated to the control and monitoringcircuitry 18 to enable determining the timing for making and/or breakingthe switching devices at a specific point on the electric powerwaveform.

As depicted, the 6-pole wye-delta starter 442 includes six switchingdevices 444, 446, 448, 450, 452, and 454 used to selectively connectthree motor windings 456, 458, and 460 to a three-phase power source(e.g., mains lines 462, 464, and 466 each carrying a single phase ofpower). In some embodiments, the first wye switching device 444, thesecond wye switching device 446, and the third wye switching device 448may have the same operational characteristics. Additionally, the firstdelta switching device 450, the second delta switching device 452, andthe third delta switching device 454 may have the same operationalcharacteristics. For example, in some embodiments, the first deltaswitching device 450, 452, and 454 may be single-pole, single currentcarrying path switching devices 218 and the wye switching devices 444,446, and 448 may be power electronic switching devices, such assilicon-controlled rectifiers (SCRs), insulated-gate bipolar transistors(IGBTs), power field-effect transistors (FETs), and/or otherbidirectional devices.

In the depicted embodiment, dashed lines are used to indicatenon-conducting pathways and solid lines are used to indicate conductingpathways. As such, FIG. 47A describes when each of the switching devices444, 446, 448, 450, 452, and 454 is open, thereby disconnecting theelectric power from the windings 456, 458, and 460. The wye-deltastarter 442 may then transition to a wye configuration using a two-stepstart sequence, as described in FIGS. 47B and 47C. From the wyeconfiguration, the wye-delta starter 442 may then transition to a deltaconfiguration using phase sequential switching, as described in FIGS.47D-H.

The steps in the phase sequential wye-delta transition using 6-polewye-delta starter 442 is essentially the same as the 5-pole wye-deltastarter 374, which is shown in FIGS. 43A-G. However, the 6-polewye-delta starter utilizes three wye switching devices (444, 446, and448), as opposed to two. As such, the order in which the wye switchingdevices are closed in the wye two-step start and the order in which thewye switching devices are opened in the phase sequential wye-deltaswitching may change. In particular, regarding the wye two-step start,in order to provide current to the windings using three wye switchingdevices, one of the steps may close two wye switching devicessimultaneously, and the other step may close the third switching device.For example, as depicted in FIG. 47B, the switching devices 446 and 448may close simultaneously to connect windings 458 and 460 from line 464to line 466. Subsequently, as depicted in FIG. 47C, the first wyeswitching device 444 may close, thereby connecting the windings 454,456, and 458 in the wye configuration.

Once the electric motor 24 is running in wye configuration, the phasesequential switching to delta may initiate. As with the 5-pole wye-deltastarter 374, one of the wye switching devices 444 may be opened as shownin FIG. 47D. Next, as shown in FIG. 47E, the first delta switchingdevice 450 may be closed to connect the first winding 456 in the deltaconfiguration. After switching device 450 closes, the motor 24 may berunning in a mixed wye-delta configuration with first winding 456connected in delta and windings 458 and 460 connected in wye. Then, asshown in FIG. 47F, the remaining two closed wye switching devices 446and 448 may be opened, for example, sequentially or simultaneously.Subsequently, switching devices 452 and 454 may be closed either oneafter the other, as shown in FIGS. 47F and 47G, or simultaneously.

It should be noted that utilizing three wye switching devices (444, 446,and 448) may enable wear balancing by keeping track of which switchingdevice(s) opened first. In some embodiments, the first switching devicethat opens may experience a larger amount of wear compared to thesubsequently opened switching devices. As such, the switching devicethat opens first may be rotated during subsequent sequential wye-deltatransitions to even out the wear on the switching devices and lengthenthe lifespan of the switching devices. In other embodiments, the orderthat the wye switching devices opens may be determined by statisticallyby randomizing the order, which may obviate persistent memory.

For example, in the depicted embodiment shown in FIGS. 47D-F, the firstwye switching device 444 may be opened first to disconnect electricpower from the first winding 456. In certain embodiments, control andmonitoring circuitry 18 connected to the wye-delta starter may recordthat the first wye switching device 444 opened first. Then, the nexttime phase sequential wye-delta switching is initiated, the control andmonitoring circuitry 18 may determine that the first wye switchingdevice 444 opened first previously and, thus, instruct the second wyeswitching device 446 or the third wye switching device 448 to openfirst. For example, since switching device 444 opened first previously,the control and monitoring system 18 may instruct the second wyeswitching to open first in a subsequent wye to delta transition.

Similar wear balancing may be performed when phase sequentiallyswitching from the delta configuration back to the wye configuration.For example, in some embodiments, the first delta switching device 450may be opened first to disconnect electric power from the first winding456. In certain embodiments, control and monitoring circuitry 18connected to the wye-delta starter may record that the first deltaswitching device 450 opened first. Then, the next time phase sequentialwye-delta switching is initiated, the control and monitoring circuitry18 may determine that the first delta switching device 450 opened firstpreviously and, thus, instruct the second delta switching device 452 orthe third delta switching device 454 to open first. For example, sinceswitching device 450 opened first previously, the control and monitoringsystem 18 may instruct the second delta switching device 452 to openfirst in a subsequent delta to wye transition.

With the foregoing in mind, FIG. 48 depicts an embodiment of a process468 for wye-delta motor starting over a series of starts. Generally, theprocess 468 includes receiving a signal to start the motor (processblock 470), selecting the switching device to close and/or open first(process block 472), executing phase sequential wye-delta switching andclose and/or open the selected switching device (process block 474), andrecording which switching device was selected and opened and/or closedfirst (process block 476). In some embodiments, process 468 may beimplemented via computer-readable instructions stored in the tangible,non-transitory memory 226, 20, 46 and/or other memories and executed viaprocessor 224, 19, 45 and/or other control circuitry.

The process 468 may enable wear balancing for various configuration ofswitching devices performing various switching operations. However, tohelp illustrate, the process 468 is described in relation to transitionfrom the wye configuration to the delta configuration using the 6-polewye-delta starter 442. For example, the control and monitoring circuitry18 may receive a signal to transition from the wye configuration to thedelta configuration (process block 470). As described above, the wyedelta starter 442 may transition from the wye configuration to the deltaconfiguration by first opening a wye switching device 444, 446, or 448.

Accordingly, the control and monitoring circuitry 18 may select one ofthe wye switching devices 444, 446, and 448 to open first (process block472). As described above, the control and monitoring circuitry 18 mayselect which wye switching device to open first based at least in parton previous open operations. For example, when the first wye switchingdevice 444 was opened first in a previous operating, the control andmonitoring system 18 may select the second wye switching device 446 orthe third wye switching device 448 to open first. Additionally, if thisis the first time switching operating, the control and monitoringcircuitry 18 may select one of the wye switching devices 444, 446, or448 as a default.

The control and monitoring circuitry 18 may instruct the selected wyeswitching device to open (process block 474). Additionally, the controland monitoring circuitry 18 may instruct the remaining switching devicesto open or close to perform the transition from the wye configuration tothe delta configuration.

Furthermore, the control and monitoring circuitry 18 may keep a recordof the selected wye switching device to facilitate determining whichswitching device to select in subsequent switching operations (processblock 476). In some embodiments, the switching device that opened firstmay be stored in memory 226, 20, or 46. In this manner, when anothersignal to transition from the wye configuration to the deltaconfiguration is received, the control and monitoring circuitry 18 mayretrieve the switching order used in the previous operation (arrow 478).

Based at least in part on the previous switching order, the control andmonitoring circuitry 18 may select a different wye switching device 444,446, or 448 to open first (process block 472). Subsequently, the controland monitoring circuitry 18 may instruct the selected wye switchingdevice to open (process block 472) and the remaining switching devicesto open or close to perform the transition from the wye configuration tothe delta configuration.

Moreover, the techniques described herein may be extended to otherwye-delta configurations. For example, FIGS. 49A and 49B depict circuitdiagrams for 8 and 9 pole wye-delta switching arrangements,respectively. In particular, the circuit diagram 480 a depicted in FIG.49A includes two wye switching devices 482 and 484 and three deltaswitching devices 486, 488, and 490, and three mains switching devices492 a, 494 a, and 496 a. Likewise, the 9-pole wye-delta starter circuitdiagram 498 a depicted in FIG. 49B includes three wye switching devices500, 502, and 504, the delta switching devices 506, 508, and 510, andthree mains switching devices 512 a, 514 a, and 516 a. As shown in thedepicted embodiments, the mains switching devices 492 a, 494 a, 496 a,512 a, 514 a, and 516 a are inside the delta configuration. Morespecifically, the mains switching devices 492 a, 494 a, 496 a, 512 a,514 a, and 516 a may be utilized as disconnect switches to isolate thewindings from the mains power when desired.

Other embodiments of the 8 and 9 pole wye-delta switching arrangementsare shown in FIGS. 49C and 49D, respectively. In particular, the circuitdiagram 480 b depicted in FIG. 49C includes two wye switching devices482 and 484 and three delta switching devices 486, 488, and 490, andthree mains switching devices 492 b, 494 b, and 496 b. Likewise, the9-pole wye-delta starter circuit diagram 498 b depicted in FIG. 49Dincludes three wye switching devices 500, 502, and 504, the deltaswitching devices 506, 508, and 510, and three mains switching devices512 b, 514 b, and 516 b. As shown in the depicted embodiments, the mainsswitching devices 492 b, 494 b, 496 a, 512 b, 514 b, and 516 b areoutside the delta configuration. The mains switching devices 492 b, 494b, 496 a, 512 b, 514 b, and 516 b may be used as disconnect switches toisolate the electric motor 24 from the mains power.

Similar to the 5 and 6 pole wye-delta switching arrangements discussedabove, the 8 and 9 pole wye-delta switching arrangements may perform thewye two-step start and the phase sequential wye-delta switching, exceptthat, before running through the openings and closings, the mainsswitching devices may be closed to provide power to the windings. Inaddition, the 8 and 9 single-pole switching arrangements may or may notutilize POW techniques to execute the wye two-step start and the phasesequential wye-delta sequencing. Also, the physical layout of thevarious wye-delta switching arrangements may be highly configurable dueto the modularity enabled by utilizing single-pole switching devices,which will be discussed in further detail below.

Motor Torque-Based Phase Sequential Switching

As noted above, a wye-delta starter (e.g., a 5-pole wye-delta starter374 or a 6-pole wye-delta starter 442) may supply electric power to anelectric motor 24 to run the motor 24 in a wye configuration or a deltaconfiguration. In should be noted that a 5-pole wye-delta starter 374may be a special case of a 6-pole wye-delta starter 442. As such,techniques applicable to a 5-pole wye-delta starter 374 may be easilyadaptable to a 6-pole wye-delta starter 44.

In some instances, when the electric motor 24 is run in wye, theelectric motor 24 may use less electric power to produce a first (e.g.,lower) torque level, and when the electric motor 24 is run in delta, theelectric motor 24 may use more electric power to produce a second (e.g.,higher) torque level. In other words, supplying electric power to theelectric motor 24 using a wye-delta starter 374 enables at least twooperating modes (e.g., less power consumption lower torque and morepower consumption higher torque).

However, there may be instances when it is desirable to operate themotor 24 somewhere between the two operating modes. For example, it maybe desirable to produce more torque than produced when operating in wye,but consume less electric power than consumed when operating in delta.In contrast, it may be desirable to produce less torque than producedwhen operating in delta, but consume more power than consumed whenoperating in wye. Thus, the wye-delta starter may sequentially traversethrough mixed wye-delta configurations to increase or decrease thetorque level and/or power consumption as desired.

To help illustrate, FIGS. 50A-F describes configurations (e.g.,open/close switching devices) of a 5-pole wye-delta starter 374 longwith corresponding torque levels produced by the electric motor 24.Turning to FIG. 50A, when the second wye switching device 378 is closed,the wye-delta starter 374 may provide two phases of electric power tothe motor windings 388 and 390. However, merely supplying two phases ofelectric power may be insufficient to rotate the electric motor 24because the resultant field cannot initiate rotation. As such, theelectric motor 24 may produce 0% of the motor's potential maximum torquelevel (e.g., in the delta configuration) and consume minimal electricpower.

As shown in FIG. 50B, when first wye switching device 376 and second wyeswitching device 378 are closed, the wye-delta starter 374 may providethree-phase power to the motor windings 386, 388, and 390. Morespecifically, in this configuration, the wye-delta starter 374 maysupply electric power to the electric motor 24 in a wye configuration.As such, the motor 24 may produces less than or equal to 33% of themotor's potential maximum torque level (e.g., in the deltaconfiguration). Additionally, in some embodiments, the power consumptionof the electric motor 24 may be less than or equal to 33% of the maximumpower consumption (e.g., in the delta configuration).

As shown in FIG. 50C, when first wye switching device 376 is opened andsecond wye switching device 378 remains closed, the wye-delta starter374 may again provide two phases of electric power to the motor windings388 and 390 in a wye configuration. However, when the motor 24 hasalready begun rotating, the two phases of electric power may besufficient to maintain rotation of the motor 24. As such, in thisconfiguration, the motor 24 may produce less than or equal to 22% of themaximum torque level and power consumption may drop to less than orequal to 22% of maximum power consumption.

As shown in FIG. 50D, when first delta switching device 380 is closedand second wye switching device 378 remains closed, the wye-deltastarter 374 may provide three-phase electric power to the motor 24. Morespecifically, the motor 24 may run in a mixed wye-delta configurationwith windings 388 and 390 connected in wye and first winding 386connected in delta. As a result, the current waveforms may beunbalanced. Nevertheless, in this configuration, the motor 24 mayproduce torque less than or equal to 55% of the maximum torque level andthe power consumption may increases to less than or equal to 55% of themaximum power consumption.

As shown in FIG. 50E, when third delta switching device 384 is closedand switching devices 380 and 378 remain closed, the wye-delta starter374 may remain providing three-phase electric power to the motor 24.More specifically, the motor 24 may continue running in a mixedwye-delta configuration with first winding 386 connected in delta,second winding 388 connected in wye, and third winding 390 connected inboth delta and wye. As such, in this configuration, the motor 24 mayproduce less than or equal to 66% of the maximum torque level and powerconsumption may increase to less than or equal to 66% of the maximumpower consumption.

As shown in FIG. 50F, when second wye switching device 378 is open,switching devices 380, 382, and 384 remain closed, the wye-delta startermay provide three-phase electric power to the motor 24 in a deltaconfiguration. As such, in this configuration, the motor 24 may produceless than or equal to 100% of the maximum torque level and powerconsumption may increase to less than or equal to 100% of the maximumpower consumption. It should be noted that throughout the phasesequential wye-delta switching steps, the torque is in the samedirection (e.g., positive).

Thus, as described above, the wye-delta starter 374 may facilitatereducing strain on the motor 24 and/or a connected load 18 by graduallyadjusting torque, particularly when starting up the motor 24. To helpillustrate, a plot 518 of torque produced when starting up a motor 24using sequential switching of a wye-delta starter is described in FIG.50G. More specifically, a motor torque curve 519 describes torqueproduced by the motor 24 between t0 and t7. In the depicted embodiment,the wye-delta starter 374 may be disconnected between t0 and t1, in theconfiguration described in FIG. 50A between t1 and t2, in theconfiguration described in FIG. 50B between t2 and t3, in theconfiguration described in FIG. 50C between t3 and t4, in theconfiguration described in FIG. 50D between t4 and t5, in theconfiguration described in FIG. 50E between t5 and t6, and in theconfiguration described in FIG. 50F between t6 and t7.

Thus, as described by the motor torque curve 519, the motor 24 mayproduce 0% of the motor's potential maximum torque level between t0 andt1 since electric power is not supplied to the windings 386, 388, and390. The motor 24 may continue producing 0% of the motor's potentialmaximum torque level between t1 and t2. More specifically, as describedabove, two phases of electric power are supplied to windings 388 and 390in a wye configuration. However, the two phases may be insufficient toinitiate rotation of the motor 24.

As described by the motor torque curve 519, the motor 24 may beginrotating and producing torque between t2 and t3. More specifically, asdescribed above, in this configuration the windings 386, 388, and 390may be connected in the wye configuration, thereby enabling the motor 24to produce less than or equal to 33% of the maximum torque level. Insome embodiments, connecting the windings 386, 388, and 390 in wye maybe a stable configuration. As such, the wye-delta starter 374 may remainin this configuration for extended durations of time.

Additionally, as described by the motor torque curve 519, the motor 24may continue rotating but produce a reduced amount of torque between t3and t4. More specifically, as described above, in this configuration thewindings 388 and 390 may remain connected in the wye configuration.However, since the motor 24 is already in rotation, the two phases ofelectric power supplied to windings 388 and 390 are sufficient tomaintain the rotation. In some embodiments, the rotation of the motor 24may begin to slow when run in this configuration for an extended period.As such, the wye-delta starter 374 may remain in this configuration fora shorter duration.

Furthermore, as described by the motor torque curve 519, the motor 24increase produced torque between t4 and t5. More specifically, asdescribed above, in this configuration windings 388 and 390 may remainconnected in wye and first winding 386 may be connected in delta,thereby enabling the motor 24 to produce less than or equal to 55% ofthe maximum torque level. In some embodiments, since electric power issupplied to teach of the windings 386, 388, and 390, this mixedwye-delta configuration may be a stable. As such, the wye-delta starter374 may remain in this configuration for extended durations of time.

As described by the motor torque curve 519, the motor 24 may againincrease produced torque between t5 and t6. More specifically, asdescribed above, in this configuration windings 388 may remain connectedin wye, first winding 386 may remain connected in delta, and thirdwinding 390 may be connected in both wye and delta, thereby enabling themotor 24 to produce less than or equal to 66% of the maximum torquelevel. In some embodiments, since electric power is supplied to teach ofthe windings 386, 388, and 390, this mixed wye-delta configuration maybe a stable. As such, the wye-delta starter 374 may remain in thisconfiguration for extended durations of time.

Additionally, as described by the motor torque curve 519, the motor 24may again increase produced torque between t6 and t7. More specifically,as described above, in this configuration windings 386, 388, and 390 mayeach be connected delta, thereby enabling the motor 24 to produce lessthan or equal to 100% of the maximum torque level. In some embodiments,connecting the windings 386, 388, and 390 in delta may be a stableconfiguration. As such, the wye-delta starter 374 may remain in thisconfiguration for extended durations of time.

Thus, in the above described example, the wye-delta starter 374 mayutilize at least four intermediate torque levels to gradually ramp upthe motor 24. In fact, a number configurations used to produce theintermediate torque levels may be stable. As such, in addition to merelyramping up the motor 24, the wye-delta starter 374 may operate the motor24 at multiple torque controlled configurations. For example, when lessthan or equal to 55% of the maximum torque is desired, the wye-deltastarter 374 may close second wye switching device 378 and first deltaswitching device 380.

As described above, power consumption of the motor 24 may correlate withconfiguration of the wye-delta starter 374. For example, powerconsumption may be greater when the connected in a delta configurationthan when connected in a wye configuration. As such, when desired torqueof the motor 24 capable of being produced by a lower stableconfiguration, the wye-delta starter 374 may transition to a lowerstable state, thereby reducing power consumption.

In other words, the steps described above regarding phase sequentialwye-delta switching may be reversed (e.g., transition from delta to anintermediate configuration) in order to reduce the amount of torqueproduced and power consumed by the motor. That is, by reversing thephase sequential wye-delta steps described, the torque and powerconsumption may be stepped down. For example, while the motor is runningin delta configuration, the second delta switching device 382 may openand the second wye switching device 378 may close. Accordingly, themotor may be running in a mixed wye-delta configuration and the torquemay reduce to less than or equal to 66% of the maximum torque level andpower consumption may reduce to less than or equal to 66% of the maximumpower consumption. Similarly, the wye-delta starter 374 may transitionto any of the intermediate configurations (e.g., stable and less stableintermediate configurations) to achieve the desired torque productionand power consumption.

Moreover, the stepwise motor torque and power consumption progressivewye-delta phase sequential switching described above provides variousbenefits to different applications. For example, a water pump may usethe disclosed techniques to slowly increase torque when switching fromwye to delta, thereby slowly increasing the amount of water delivered topipes, as opposed to turning the pump on full bore immediately andblasting water through the pipes. This may increase the lifespan of thepipes. In addition, it may be desirable to put certain loads in a powersave mode but still keep the motor running. Thus, if the motor 24 isrunning in delta, it can reverse the sequential steps, as mentionedabove, and ramp down the amount of power consumed until a desired amountis reached. As may be appreciated, the techniques disclosed hereinenable configuring the amount of torque produced and power consumed bythe motor 24 as desired by utilizing single-pole devices (e.g.,single-pole, single current-carrying path switching devices 218) in aphase sequentially transition.

As such, the configuration of the motor starter (e.g., which switchingdevices are open and which switching devices are closed) may be based ona desired output torque level or a desired power consumption. As such,one embodiment of a process 520 for determining configuration of theswitching devices in the motor starter based on a desired torque levelis shown in FIG. 51A. Generally, process 520 includes selecting adesired torque level (process block 522), determining a configuration ofthe motor starter based on the desired torque level (process block 524),and setting the configuration (process block 526). In some embodiments,the process 520 may be implemented via computer-readable instructionsstored in a non-transitory article of manufacture (e.g., the memory 226,20, 46 and/or other memories) and executed via processor 224, 19, 45and/or other control circuitry.

Accordingly, control circuitry 18 may determine the desired torque levelto be produced by the motor 24 (process block 522). More specifically,in some embodiments, the desired torque level may be input to thecontrol circuitry 18 by a user. In other embodiments, the desired torquelevel may be pre-configured in the control circuitry 18. For example,certain loads may be started and the amount of torque produced may beincrementally increased by the control circuitry 18 over a period oftime in order to gradually ramp up to 100% torque produced in delta.Alternatively, it may be desirable to reduce the amount of torque a loadis producing if it has been running for a certain period of time, and,thus, the control and monitoring circuitry 18 may select a reducedtorque level to produce.

In any embodiment, after the desired torque is determined, the controland monitoring circuitry 18 may determine the configuration to applybased upon the desired torque level (process block 524). As describedabove with reference to FIGS. 50A-F, each step of the phase sequentialswitching may produce a different amount of torque. For example, whenthe motor is running in a wye configuration supplying three-phase powerto all three windings, less than or equal to 33% torque may be produced(FIG. 50B). When the motor is running in a mixed wye-delta configurationwhere two windings are in wye and one winding is in delta, less than orequal to 55% torque may be produced (FIG. 50D). Also, when one windingis in delta, one winding is in wye, and one winding is in both wye anddelta, less than or equal to 66% torque may be produced (FIG. 50E), andwhen the motor is running in delta, less than or equal to 100% torquemay be produced (FIG. 50F). Thus, the control and monitoring circuitry18 may select the configuration that achieves the desired torque level.

In alternative embodiments, if the desired torque is not exactly one ofthe possible options, the control and monitoring circuitry may determinewhich configuration most closely achieves the desired torque. Forexample, the control and monitoring circuitry 18 may round the torque upor down based on which available torque values are provided by thedifferent configurations. More specifically, if a user desires theelectric motor 24 to produce 40% torque and the two closest availabletorque options are 33% and 55% torque production, the control andmonitoring circuitry 18 may round down to 33% because it is closer to40% than 55%. As a result, the control and monitoring circuitry 18 mayselect the wye configuration depicted in FIG. 50B to apply to achievethe torque closest to the desired 40% torque. Additionally oralternatively, the control and monitoring circuitry 18 may round up to55% torque to ensure that sufficient torque is provided.

In further embodiments, the control and monitoring circuitry 18 mayperiodically alternate between any two torque states to achieve thedesired (e.g., intermediate) torque level. More specifically, theduration at each of the two torque states may adjust the resultingtorque level. For example, to produce a torque level of 60.5%, thecontrol and monitoring circuitry 18 may operate the wye-delta starter374 in a first mixed wye-delta configuration that produces 55% torquewith a 50% duty cycle and a second mixed wye-delta configuration thatproduce 66% torque with a 50% duty cycle. In this manner, variousintermediate torque levels may be produced, which may be particularlyuseful for high inertia loads like long conveyer lines and long sectionsof pipe (e.g., a water hammer).

Once the configuration is determined, the control and monitoringcircuitry 18 may set the selected configuration by instructing theswitching devices to open or close to implement the determinedconfiguration (process block 526). It should be noted that in someembodiments, determined configuration may be implemented with POWtechniques. As described above, utilizing POW techniques may prolong thelife span of the switching devices.

It should be further noted that, in some embodiments, the switchingdevices may be opened or closed in accordance with the phase sequentialwye-delta switching. In other words, the control unit 18 may determinethe state (e.g., open or closed) of each of the switching device andsequentially instruct each of the switching devices to open, close, ormaintain its current state. To help illustrate, if 55% torque level isselected and the motor is started, the control and monitoring circuitry18 may sequentially open and close the switching device, in accordancewith the phase sequential switching, to set the motor in the mixedwye-delta configuration that achieves 55% torque level. Likewise, if themotor is running in delta (e.g., 100% torque) and a lower torque isselected, the control and monitoring circuitry 18 may determine and seta different configuration by reverse the steps in the phase sequentialwye-delta switching. Additionally or alternatively, once theconfiguration is determined, the control circuitry 18 may instruct theswitching devices to implement the configuration in any order, forexample, simultaneously.

Similarly, one embodiment of a process 530 for determining configurationof the switching devices in the motor starter based on a desired powerconsumption is shown in FIG. 51B. Generally, process 530 includesselecting a desired power consumption (process block 532), determining aconfiguration of the motor starter based on the desired powerconsumption (process block 534), and setting the configuration (processblock 536). In some embodiments, the process 530 may be implemented viacomputer-readable instructions stored in a non-transitory article ofmanufacture (e.g., the memory 226, 20, 46 and/or other memories) andexecuted via processor 224, 19, 45 and/or other control circuitry.

As can be appreciated, process 530 includes many of the same processingsteps as process 520. Specifically, the control circuitry 18 maydetermine a desired power consumption (process block 532). In someembodiments, the control and monitoring circuitry 18 may select thepower consumption level based upon the type of load, pre-configuredpower modes (e.g., power save mode), power consumption schedules, and soforth. For example, the control circuitry 18 may determine amount ofpower consumption based on the amount of power available. In otherwords, if the control and monitoring circuitry 18 determine that a highamount of power is available, the control and monitoring circuitry 18may determine that the maximum power consumption may be utilized. On theother hand, if the control and monitoring circuitry 18 determine that alow amount of power is available, the control and monitoring circuitry18 may determine that a power consumption less than the maximum shouldbe utilized.

As described with reference to FIGS. 50A-F, each varying configurationin the wye-delta starter may result in different power consumptions.Thus, the control and monitoring circuitry 18 may determine the motorconfiguration based upon the desired power consumption level (processblock 534). That is, the control and monitoring circuit 18 may selectthe configuration (e.g., wye, mixed wye-delta, delta, etc.) thatconsumes the desired amount of power. The control and monitoringcircuitry 18 may then instruct the switching devices to implement thedetermined configuration.

Based on the above, the described techniques enables running a wye-deltamotor starter with varying torque levels and varying power consumptionssimply by opening and closing switching devices in the motor starter.

Operator-Initiated Point-on-Wave Switching

As used in the various operations described herein, switching device 218may be used to selectively connect and/or disconnect electric power froma load 14. For example, in a close operation, switching devices 218 maybe used to connect three-phase electric power to an electric motor 24 ina manner that reduces electric arcing. More specifically, as describedabove, two phases may be connected at a first time in coordination witha predicted current zero-crossing and the third phase may be connectedbased upon a subsequent predicted current zero-crossing. In other words,the switching device 218 may close at specific points on the electricpower waveform.

In some embodiments, the various operations may be initiated by anoperator. For example, an operator may instruct the switchgear 16 toconnect electric power to the load 14 via a human-machine interface onthe control and monitoring circuitry 18. Accordingly, the operatorinstruction may be received at any suitable time during operation viathe network 21. In other words, different operator instructions may bereceived independent of the electric power to be connected ordisconnected from the load. Thus, to perform the operator initiatedoperation at specific points on the electric power waveform, the controland monitoring circuitry 18 may take into account the unpredictablenature of when an operator instruction is received.

To help illustrate, FIG. 52 depicts a source voltage waveform 540 of onephase of electric power supplied by the power source 12 during anoperator-initiated make operation. As described above, an operatorinstruction to make may be received independent from the source voltage540. In other words, in the depicted embodiment, the operatorinstruction may be received at some time before tR. To account for theunpredictable timing of receiving the operator instruction, a referencepoint 542 in the future may be selected. In the depicted embodiment, thereference point 542 corresponds to a voltage zero-crossing (e.g., apredicted current zero-crossing) at tR. In other embodiments, anysuitable reference point may be used.

From the reference point 542, the close operation may be performed. Morespecifically, as described above, the processor 224 may determine theexpected make time 544 of the switching device 218. The processor 224may determine a specific point 546 that is at least the expected maketime later than the reference point 542 to enable the switching device218 to close at the specific point 546. Additionally, the processor 224may determine when to apply the current profile (e.g., pull-in current)to the operating coil 220 to make at the desired point 546 and instructthe operating current to apply the current profile at the determinedtime.

More generally, a process 548 for performing an operator-initiatedoperation is shown in FIG. 53. The process 548 may be implemented viacomputer-readable instructions stored in the tangible non-transitorymemory 226, 20, 46 and/or other memories and executed via processor 224,19, 45 and/or other control circuitry. Generally, the process 548includes receiving an operator instruction (process block 550),determining the electric power waveform (process block 552), selecting areference point (process block 554), and initiating the operation(process block 556).

In some embodiments, the control and monitoring circuitry 18 may receivethe operator instruction via a human-machine interface, such as akeyboard or a push button, at any suitable time during operation(process block 550). More specifically, the operator instruction maycontain an instruction to perform a specific operation. For example, theoperator may instruct the wye-delta starter 374 to transition from wyeto delta. Accordingly, the control and monitoring circuitry 18 maydetermine what operation to perform based on the operator instruction.

Additionally, as described above, the operation may be carried out bymaking and/or breaking switching devices 218 at specific points on theelectric power waveform. Accordingly, the control and monitoringcircuitry 18 may determine the electric power waveforms based on sensormeasurement feedback (process block 552). More specifically, the controland monitoring circuitry 18 may determine particular electric powerwaveforms based on the operation that will be performed. For example,when the operation is a make operation, the control and monitoringcircuitry 18 may determine the source voltage waveform. Additionally,when the operation is a break operation, the control and monitoringcircuitry 18 may determine the current voltage waveform.

It should be noted that although the depicted embodiment depicts thatthe electric power waveform is determined in response to the operatorinstruction, additionally or alternatively, the control and monitoringcircuitry 18 may continuously determine the electric power waveforms. Inother words, the electric power waveforms may be determined regardlessof whether an operator instruction is received. For example, the controland monitoring circuitry 18 may determine the source voltage waveformand the source current waveform throughout operation. In someembodiments, continuously determining the electric power waveforms mayenable diagnostics on the source 12, the switching device 218, the load14, or any combination thereof.

On the electric power waveform, the control and monitoring circuitry 18may then select a reference point 542 in the future (process block 554).As described above, the reference point may be used to account for theunpredictable timing of the operator instruction. Accordingly, in someembodiments, the reference point 542 may be selected based on repeatablecriteria to enable the operation to be initiated from a predictablestarting point. For example, the reference point 542 may be selectedfrom the future voltage zero-crossings on the electric power waveform.

From the reference point, the control and monitoring circuitry 18 mayinitiate the operation (process block 556). More specifically, thecontrol and monitoring circuitry 18 may determine which switching device218, and more specifically which operating coil driver circuitry 222,will be used to carry out the operation. Additionally, the control andmonitoring circuitry 18 may determine the desired make times and/ordesired break times for each switching device 218. As described above,the desired make times and desired break times may be specific points onthe electric power waveform. In other words, the control and monitoringcircuitry 18 may coordinate the switching of the various switchingdevice 218 at specific points on a wave to perform the operation. Asdescribed herein, examples of the operation may include closingswitching devices 218, opening switching devices 218, transitioning fromwye to delta, transitioning from delta to wye, setting a specific torqueor power level, reversing an electric motor 24, or bypassing a load,such as a motor drive.

It should be noted that there are certain asymmetrical edge conditionsthat may be taken into consideration when attempting to break ahead of acurrent zero-cross and/or when setting the electrical degree separationsof making and breaking the switching devices. For example, if theselected reference point or amount of electrical degrees actually causesan opening to occur after a current zero-crossing there may bepenalizing consequences. In fact, missing a current zero-crossing markwhen breaking may increase arcing because a half line cycle ofincreasing current is applied during the opening in the switching deviceand the stronger arc may prevent the switching device from opening.Thus, it may be desirable to miss the mark short of the currentzero-crossing and open when the current is going downward on a halfcycle to the current zero-cross, as opposed to missing the mark afterthe current zero-crossing.

Additionally or alternatively, the control and monitoring circuitry 18may determine whether to perform process 548 based on the importance ofthe operator instruction. For example, although the switching device 218may break at specific points on a wave to reduce electric arcing, it maybe desirable to remove electric power from the load 14 as soon aspossible. In other words, the control and monitoring circuitry 18 maydetermine the importance of the operator instruction and weigh theimportance against the consequences of performing the operation at anypoint on the wave.

Synchronous Re-Closure

As described above, one or more switching devices 218 may be used toconnect and/or disconnect electric power from an electric motor 24. Forexample, electric power may be connected to rotate the electric motor24. Once the electric motor 24 is spinning, electric power may bedisconnected from the electric motor 24 for various reasons. Even thoughelectric power is removed, the momentum of the electric motor 24 and anyload actuated by the motor (e.g., a fan 47, a conveyer belt 48, or apump 50) may keep rotating the electric motor 24 while friction beginsto slow the electric motor 24. As the electric motor 24 continues torotate, a back electromotive force (EMF) is generated. In other words,the electric motor 24 acts as a generator to produce a voltage (e.g.,back EMF) with a changing frequency.

To restart the electric motor 24, electric power may be reconnected tothe electric motor 24. In some embodiments, it may be desirable torestart the electric motor 24 as soon as possible. For example, if anelectric motor 24 in a chiller 54 completely stops, the gas and liquidrefrigerant in the chiller 54 may become displaced. Thus, to restart theelectric motor 24 may take an inconvenient period of time. Accordingly,electric power may be reconnected while the electric motor 24 is stillrotating. As described above, the electric motor 24 generates a back EMFwith a changing frequency commensurate with it rotational frequencywhile it is rotating. However, since the frequency is changing, the backEMF and the electric power to be reconnected to electric motor 24 may beout of phase. In some embodiments, when electric power is reconnectedwhile the electric power is lagging behind the back EMF, negative torquemay be generated in the electric motor 24, which may decrease thelifespan of the motor and/or a connected load or result in surgecurrents that trip protection circuitry.

Accordingly, one embodiment of the present disclosure describes a methodfor synchronously re-closing (i.e., reconnecting) electric power to anelectric motor 24. More specifically, the method includes starting acounter when either the source electric power or the back EMF crosseszero volts (i.e., voltage zero-crossings) and stopping the counter atthe next subsequent voltage zero-crossing. Additionally, the methodincludes monitoring the counter value trend to determine whether thesource electric power or the back EMF is leading. Furthermore, themethod includes reconnecting the source electric power while it isleading the back EMF based at least in part on the counter value trend.More specifically, the source electric power may be reconnected at orafter a local minimum in the counter value trend. In other words, thelocal minimum in the counter value trend may indicate when the sourceelectric power switches from lagging to leading the back EMF. Thus,reconnecting at or after a local minimum facilitates reconnecting thesource electric power when it is leading the back EMF, which reduces thechances of producing negative torque when re-closing. Additionally, itmay be beneficial to begin using the counter to monitor voltagezero-crossings as soon as the electric motor is disconnected to reducethe likelihood of the electric power and the EMF from being 180° out ofphase when re-closing.

To help illustrate, FIG. 54 is a plot that depicts the source electricpower voltage waveform 558 and the back EMF voltage waveform 560 for onephase. As can be appreciated, the waveforms for the other two phases ofthree-phase electric power will be offset by 120 degrees. In someembodiments, the waveforms may be determined based on measurementsgathered by sensors 22 that monitor voltage at the power source 12 andsensors 22 that monitor voltage at the electric motor 24. Additionally,FIG. 54 depicts the counter value 562.

As depicted, the source voltage 558 and the back EMF voltage 560 havedifferent frequencies. Thus, over time, the source voltage 558 and theback EMF voltage 560 will drift into and out of phase from one another.For example, at t1, the source voltage 558 is leading the back EMFvoltage 560. As the phases drift past each other, at t4, the sourcevoltage 558 transitions from leading to lagging behind the back EMFvoltage 560. As used herein, “leading” is generally intended to describewhen one waveform is between 0 to 180 degrees ahead of a subsequentwaveform, and “lagging” is generally intended to describe when onewaveform is between 0 to 180 degrees behind a preceding waveform.

Thus, to facilitate reconnecting the source electric power when thesource voltage 558 is leading the back EMF voltage 560, the control andmonitoring circuitry 18 (e.g., processor 224) may determine when thesource voltage 558 transitions from lagging to leading. In someembodiments, the control and monitoring circuitry 18 may utilize acounter, such as a free running counter (FRC) included in the processor224, to facilitate keeping track of the transitions.

More specifically, the counter may be started at either a source voltage558 zero-crossing or a back EMF voltage 560 zero-crossing. The countermay continue counting until a subsequent voltage zero-crossing isreached. For example, the source voltage 558 zero-crossing at t1 startsthe counter. As the counter runs, the counter value 562 continues toincrease. The counter stops at the next subsequent voltagezero-crossing, which is the back EMF voltage 560 zero crossing at t2.After t2, the counter value 562 is reset. Thus, the counter value 562may be used to indicate the time difference between adjacent voltagezero-crossings. In other words, the counter value 562 at t2 indicatesthe lead the source voltage 558 has over the back EMF voltage 560 (e.g.,time difference between t1 and t2). Since the frequency of the sourcevoltage 558 is higher than the back EMF voltage 560, the sourcevoltage's lead over the back EMF voltage 560 continues to increase.Accordingly, as depicted, the trend of the counter value 562 isincreasing when the source voltage 558 is leading.

It is noted that the counter may stop at any subsequent voltagezero-crossing. For example, the source voltage 558 zero-crossing at t3starts the counter and the counter value 562 increases until thesubsequent source voltage 558 zero-crossing at t4. In other words, thecounter is started and stopped by the same voltage waveform. Thus, thecounter value 562 at t4 is at a maximum and corresponds with half theperiod of the source voltage 558 (e.g., 180 degrees). In other words,the source voltage 558 is ahead of the back EMF voltage 560 by more than180 degrees. Thus, based on the definitions above, the source voltage558 has transitioned to lagging behind the back EMF voltage 560. Inother words, a local maximum of the counter value 562 trend indicatesthe transition of the source voltage 558 from leading to lagging behindthe back EMF voltage 560.

Accordingly, after t4, the source voltage 558 is lagging behind the backEMF voltage 560. As described above, the frequency of the source voltage558 is higher than the back EMF voltage 560. In other words, the sourcevoltage 558 lag behind the back EMF voltage 560 continues to decrease.Accordingly, as depicted, the trend of the counter value 562 isdecreasing when the source voltage 558 is lagging.

As the amount of lag continues to decrease, the source voltage 558eventually overtakes the back EMF voltage 560 and transitions to leadingthe back EMF voltage 560. Similar to the transition from leading tolagging, the transition from lagging to leading may be based on thecounter value 562 trend. For example, minimum amount of lag occurs att5. Accordingly, as depicted, a first minimum counter value 562 occursat t5. Thus, the source voltage 558 will shortly thereafter transitionto leading the back EMF voltage 560. Additionally, as depicted, a secondminimum counter value 562 occurs at t6 because the source voltage 558has transitioned to slightly leading the back EMF voltage 560. In otherwords, a local minimum of the counter value 562 trend indicates thetransition of the source voltage 558 from lagging to leading the backEMF voltage 560.

Accordingly, the electric power may be reconnected to the electric motor24 when the source voltage 558 is leading the back EMF voltage 560 basedat least in part on the counter value 562. One embodiment of a process564 for reconnecting electric power to the electric motor 24 is shown inFIG. 55. Generally, the process 564 includes starting a counter at asource voltage zero-crossing or a back EMF voltage zero-crossing(process block 566), stopping the counter at the next source voltagezero-crossing or back EMF voltage zero-crossing (process block 568),monitoring the counter value trend (process block 570), and reconnectingelectric power after a local minimum in the counter value trend (processblock 572).

In some embodiments, the processor 224 included in the operating coildriver circuitry 222 may be used to execute the process 564. Asdescribed above, the counter used may be included in the processor 224.Accordingly, the processor 224 may start the counter when it detects asource voltage 558 zero-crossing or a back EMF voltage 560 zero-crossing(process block 566). Additionally, the processor 224 may stop thecounter when it detects a next subsequent source voltage 558zero-crossing or a back EMF voltage 560 zero-crossing (process block568). To facilitate detecting the voltage zero-crossings, sensors 22that monitor voltage at the power source 12 and/or the electric motor 24may feedback measurements to enable the processor 224 to determine thesource voltage 558 and the back EMF voltage 560.

Additionally the processor 224 may monitor the trend of the countervalue 562 (process block 570). More specifically, the processor 224 maystore the counter value 562 each time the counter stops, for example inmemory 226. Additionally, the processor 224 may store a timecorresponding with when each counter value 562 was stopped. Thus, theprocessor 224 may determine the trend of the counter value 562 bylooking at the previously stored counter values 562. For example, inchronological order, a first counter value, a second counter value, anda third counter value may be stored. Thus, when the second counter valueis less than the first counter value and the third counter value, theprocessor 224 may determine that a local minimum occurs at the timecorresponding with the second counter value. On the other hand, when thesecond counter value is higher than the first counter value and thethird counter value, the processor 224 may determine that a localmaximum occurs at the time corresponding with the second counter value.

Based on the counter value 562 trend, electric power may be reconnectedafter a local minimum (process block 572). As discussed above, theprocessor 224 may determine when a local minimum occurs. Accordingly,once the local minimum is detected, the processor 224 may reconnectelectric power to the electric motor 24. In some embodiments, theprocessor 224 may instruct the operating coil driver circuitry 222 tore-close the switching device 218, which may include setting theoperating coil current 250 to the pull-in current. More specifically,once it is determined that the source voltage 558 is leading, theprocessor 224 may execute process 258 to re-close the switching device218 at a desired time to make, for example, based upon a predictedcurrent zero-crossing, as described above. Additionally oralternatively, other means for reconnecting the electric power may beused, such as insulated-gate bipolar transistors.

As described above, when the trend of the counter values 562 isincreasing, the source voltage 558 is leading the back EMF voltage 560.Thus, if the switching device 218 is closed between t1 to t4, electricpower will be reconnected while the source voltage 558 is leading theback EMF voltage 560. However, the amount the source voltage 558 leadsthe back EMF voltage 560 may affect the increase in positive torquegenerated in the electric motor 24 when electric power is reconnected.Accordingly, to limit the positive torque produced, a threshold countervalue may be used. For example, if trend is increasing (e.g., after alocal minimum) and the counter value 562 is less than the thresholdvalue, the switching device 218 may be closed. On the other hand, ifcounter value 562 is greater than the threshold value, the switchingdevice 218 may wait for a subsequent local minimum to close.

Additionally, as discussed in previous sections, the make operation ofthe switching device 218 is generally not instantaneous. In other words,the source voltage 558 may be leading the back EMF voltage 560 by alarger amount than when the local minimum was detected. In mostembodiments, the amount of torque generated when the source voltage 558leads the back EMF voltage 560 by between 0-90 degrees will notnegatively affect the electric motor 24. Accordingly, the thresholdcounter value may be reduced to account for the delay.

Nevertheless, in some embodiments, the processor 224 may predict when alocal minimum in the counter value 562 will occur. More specifically,the processor 224 may predict the next local minimum based on the loadactuated by the electric motor 24. For example, when the electric motor24 is actuating a pump 50, the electric motor 24 may slow according to asquare log curve. Thus, the processor 224 may determine how thefrequency of the back EMF voltage 560 generated by the motor willchange, which then may be used to predict when the next local minimumwill occur.

In fact, in some embodiments, the processor 224 may determine the typeof load the electric motor 24 is actuating based at least in part onwhere the local minimums occur. For example, when the occurrence of thelocal minimums quickly decreases, the processor 224 may determine thatthe frequency of the back EMF voltage 560 is quickly decreasing. Assuch, the processor 224 may determine the relative magnitude of theinertia of a load.

As can be appreciated, the techniques described above may be utilizedfor reconnecting multiple phases of electric power. For example, process564 may be executed with regard to each phase independently.Additionally or alternatively, since each phase of the source voltage558 and the back EMF voltage 560 will be proportionally offset (e.g., by120 degrees) from one another, the counter may be utilized on a singlephase. More specifically, when the processor 224 determines that onephase of the source voltage 558 is leading the back EMF voltage 560, theother phases of the source voltage 558 will also be leading. Thus, insome embodiments, each phase may be connected substantiallysimultaneously. Accordingly, this may be useful in an opennon-sequential wye-delta starter. For example, after the wye connectionsopen, the electric motor 24 will continue rotating. To close the deltaconnections, the processor 224 may determine when the source voltage 558is leading the back EMF voltage 560 by examining a single phase.

Switch-Based Detection of Motor Conditions

Utilizing the single-pole switching devices (e.g., single-pole, singlecurrent-carrying path switching devices 218 described above) may enableincreasing the amount of control over the electric power supplied to theelectric motor 24. For example, the single-pole switching devices mayenable independently controlling each phase of supplied three-phasepower, which may enable detection of faults (e.g., a phase-to-groundshort or a phase-to-phase short) while minimizing duration of the faultycondition and amount of energy present during the faulty condition. Aswill be described in detail herein, in some embodiments, faults (e.g., ashort circuit) may be detected by applying a very brief, low voltagepulse (e.g., lower than the line voltage) to the motor 24 at a point onthe sinusoidal waveform coordinated with a voltage zero-crossing. Thepulse may be applied for a minimal time sufficient for fault detection.Thus, if a short circuit exists, the energy remains relatively small dueto the low voltage and short duration. As a result, the fault may becleared without tripping any connected circuit breakers, and bedetrimental to the electric motor 24 and its windings may be reduced.

Examples of faulty motor conditions that may be detected using thedisclosed techniques include a phase-to-ground short, a phase-to-phaseshort, and a phase-to-phase open circuit, among others. Aphase-to-ground short may occur when the insulation to ground hasdeteriorated and current flows into the ground, for example, in awinding of a motor. A phase-to-phase short may occur when phases comeinto contact without any load or resistance, such as when wires havebeen connected improperly (e.g., two phases wired together), an externalobject has been laid across the wires, two motor windings are shorted,and so forth. Additionally, a phase-to-phase open circuit may occur whenwindings in a motor are disconnected or otherwise open circuited.

To determine whether such faults exist, a technique referred to as“sniffing,” herein, may be employed. Generally, as will be described inmore detail below, sniffing may be defined as momentarily connecting aphase of electrical power to test for a phase-to-ground short and/ormomentarily connecting two phases of electrical power to test forphase-to-phase faults. Depending on the load being started, thesetechniques may be performed before each start or may be performedintermittently over a plurality of starts or during commissioning of anew or revised installation.

The benefits of using the techniques before starting may extend thelifespan of a load (e.g., electric motor 24) by supply power to the loadadvantageous for protection circuitry to handle potential faultcurrents. In fact, in some embodiments, different trip behavior may beused during the sniffing process. For example, the protection circuitrymay use a higher protection scheme (e.g., more sensitive) when sniffingand return to a normal protection scheme thereafter. In this manner, anyresults of a possible fault detection during sniffing may be moreeffectively mitigated by the protection circuitry.

With the foregoing in mind, FIG. 56A is a diagrammatical representationof circuitry for detecting motor conditions utilizing single-poleswitching devices and a corresponding timing diagram, respectively.Although single-pole, single current-carrying path switching devices aredescribed, any other type of switching device, such as a three-phaseoffset pole switching device, may be used.

As depicted in the motor system 574, a power source 12 providesthree-phase electric power to an electric motor 24 via three single-poleswitching devices (576, 578, and 580), one for each phase. It should benoted that the single-pole switching devices may include thesingle-pole, single current path switching devices described above(e.g., contactors, relays, etc.). Additionally or alternatively,single-pole, multiple current-carrying path switching devices may beused. Each phase may be connected to a separate winding on the motor 24via separate motor terminal. Further, the electric motor 24 may beconnected to the ground 582.

In some embodiments, the operation (e.g., opening or closing) of thesingle-pole switching devices may be controlled by control andmonitoring circuitry 18. In other words, the control and monitoringcircuitry 18 may instruct the single-pole switching devices (576, 578,and 580) to connect or disconnect electric power. Additionally, asdepicted, the control and monitoring circuitry 18 may be remote from thesingle-pole switching devices (576, 578, and 580). In other words, thecontrol and monitoring circuitry 18 may be communicatively coupled tothe single-pole switching devices (576, 578, and 580) via a network 21.In some embodiments, the network 21 may utilize various communicationprotocols such as DeviceNet, Profibus, or Ethernet. The network 21 mayalso communicatively couple the control and monitoring circuitry 18 toother parts of the system 574, such as other control circuitry or ahuman-machine-interface (not depicted). Additionally or alternatively,the control and monitoring circuitry 18 may be included in thesingle-pole switching devices (576, 578, and 580) or directly coupled tothe single-pole switching devices, for example, via a serial cable.

Furthermore, as depicted, the electric power output from the single-poleswitching devices (576, 578, and 580) may be monitored by sensors 22.More specifically, the sensors 22 may monitor (e.g., measure) thecharacteristics (e.g., voltage or current) of the electric power.Accordingly, the sensors 22 may include voltage sensors and currentsensors. Additionally, the characteristics of the electric powermeasured by the sensors 22 may be communicated to the control andmonitoring circuitry 18 to generate waveforms (e.g., voltage waveformsor current waveforms) that depict the electric power. The waveformsgenerated based on the sensors 22 monitoring the electric power outputfrom the single-pole switching devices (576, 578, and 580) and suppliedto the motor 24 may be used in a feedback loop to, for example, monitorconditions of the motor 24.

For example, the sensors 22 may sense whether current is flowing whenany of the single-pole switching devices (576, 578, and 580) close andreport this information to the control and monitoring circuitry 18. Ifcurrent is flowing, the control and monitoring circuitry 18 may thendetermine how much current is flowing by generating a graph thatanalyzes change in current (di) versus change in time (dt), which may bereferred to as the “di/dt slope.” In some embodiments, the control andmonitoring circuitry 18 may look at the change in voltage (dv) versuschange in time (dt) to determine the current. As will be explained indetail below, sensing whether current is flowing and determining thechange in the current (e.g., di/dt slope) may enable detecting whether aphase-to-ground short or phase-to-phase fault is present.

Turning now to the operation of the sniffing process, which may beutilized in some embodiments to detect phase-to-ground faults, thecontrol and monitoring circuitry 18 may utilize POW techniques todetermine a desired point on the waveform to close ahead of a voltagezero-crossing. That is, each phase output by the power source 12, thecontrol and monitoring circuitry 18 may analyze the phase voltage todetermine when it will cross zero on the voltage waveform and pick adesired point to close a few electrical degrees before thatzero-crossing. Then, the control and monitoring circuitry 18 may apply avery brief, low line voltage pulse (e.g., lower than the line voltage)to the motor 24 by closing the switching device at the desired point onthe wave and quickly (e.g., milliseconds) opening the single-poleswitching device. One reason to close a few electrical degrees ahead ofa voltage zero-crossing (e.g., on the downward slope of a positive halfcycle on the AC waveform) is so that the energy remains small if a shortcircuit exists due to the low voltage and short duration of the closure.If there is any current (e.g., not zero) sensed by the sensors 22, thena phase-to-ground fault may be present because the ground has closed thecircuit and current is flowing. However, if there is zero current sensedby the sensors 22, then there may not be a phase-to-ground faultpresent.

This process may be utilized to test each phase independently. Forexample, the control and monitoring circuitry 18 may determine a desiredpoint on the phase A waveform to close ahead of a voltage zero-crossingand then send a signal to the single-pole switching device 576 to closeaccordingly. Very quickly thereafter (e.g., a few milliseconds), thesingle-pole switching device 576 may be instructed to open by thecontrol and monitoring circuitry 18 and the control and monitoringcircuit 18 may be notified if current is sensed by the sensor 22. If acurrent is sensed, this may indicate that a phase-to-ground short ispresent in the motor system 574. More specifically, if any current(e.g., not zero) is sensed by the sensors a short may be present in awinding of the motor 24 that receives phase A or an interconnect thatcarries phase A to the motor 24.

Additionally, the control and monitoring circuitry 18 may determine adesired point on the phase B waveform to close ahead of a voltagezero-crossing and then sending a signal to the single-pole switchingdevice 578 to close accordingly. Very quickly thereafter (e.g., a fewmilliseconds), the single-pole switching device 578 may be instructed toopen by the control and monitoring circuitry 18 and the control andmonitoring circuit 18 may be notified if current is sensed by the sensor22. More specifically, if any current (e.g., not zero) is sensed by thesensors a short may be present in a winding of the motor 24 thatreceives phase B or an interconnect that carries phase B to the motor24.

Furthermore, the control and monitoring circuitry 18 determine a desiredpoint on the phase C waveform to close ahead of a voltage zero-crossingand then sending a signal to the single-pole switching device 580 toclose accordingly. Very quickly thereafter (e.g., a few milliseconds),the single-pole switching device 580 may be instructed to open by thecontrol and monitoring circuitry 18 and the control and monitoringcircuit 18 may be notified if current is sensed by the sensor 22. Morespecifically, if any current (e.g., not zero) is sensed by the sensors ashort may be present in a winding of the motor 24 that receives phase Cor an interconnect that carries phase C to the motor 24. Additionally,if a phase-to-ground fault is detected, it may be desirable to delaystarting the motor so that the fault may be remedied and detriment tothe motor, load, and/or power circuit may be inhibited.

To help illustrate, the duration of each switching device closing andopening, FIG. 56B presents a timing diagram of the operations. Asdepicted, the y-axis represents the voltage applied to the coil, and thex-axis represents the amount of time in milliseconds. The graph showsall three phases being briefly pulsed and tested consecutively. A firstphase-to-ground fault detection begins by closing the single-poleswitching device 576 at t1 and opening the single-pole switching device576 at t2. As may be seen, the elapsed time that the single-poleswitching device 576 remained closed between t1 and t2 is very brief(e.g., a few milliseconds). In other words, the switching device 576 ispulsed to detect phase-to-ground shorts related to phase A.

Similarly, a second phase-to-ground fault detection begins by closingthe single-pole switching device 578 at t3 and opening the single-poleswitching device 578 at t4, which is a few milliseconds after at t3. Assuch, the switching device 578 is pulse to detect phase-to-ground shortsrelated to phase B. Additionally, a third phase-to-ground faultdetection begins by closing the single-pole switching device 580 at t5and opening the single-pole switching device 580 at t6, which is a fewmilliseconds after t5. As such, the switching device 580 is pulsed todetect phase-to-ground shorts related to phase C.

As described above, a low amount of voltage applied briefly to the motorsystem 574 during the phase-to-ground testing because the switchingdevices 576-580 are closed near a voltage zero-crossing for each phase.Accordingly, low voltage and brief duration may reduce likelihood ofcircuit breakers tripping, as well as reduce detriments to the motor andits windings in the instance that a phase-to ground short is present.

Additionally, as described above, the sniffing process may also beutilized to detect phase-to-phase shorts utilizing the system 574 inFIG. 56A. For example, the control and monitoring circuitry 18 may closeand open a single-pole switching device that supplies a first phase ofelectric power and a single-pole switching device that supplies a secondphase of electric power one after the other such that there is a briefoverlap between when single-pole switching devices are closed. Morespecifically, the switching devices may be pulsed when at aphase-to-phase predicted current zero-crossing. In some embodiments, aphase-to-phase predicted current zero-crossing may occur phase-to-phasevoltage is at a maximum. In some embodiments, the single pole switchingdevices arranged in a delta configuration of a wye-delta motor startermay be used to detect for phase-to-phase shorts.

Based on the current measured by the sensors 22, the control andmonitoring circuitry 18 may determine if a phase-to-phase fault ispresent. More specifically, if no current is sensed, a phase-to-phaseopen circuit may be present in the motor system 574 and requiremaintenance. On the other hand, if a current is sensed, the control andmonitoring circuitry 18 may determine and analyze the change in thecurrent (e.g., di/dt slope). More specifically, a nearly vertical (e.g.,rapidly increasing) di/dt slope may indicate that a phase-to-phase shortis present. In some embodiments, the phase-to-phase short may be causedby the interconnects being in contact without a load or the windings areshorted. When a phase-to-phase short is present, the motor windings maybe inspected to check the wiring before starting. If the di/dt slope ischanging over time or has some angle to it, the control and monitoringcircuitry 18 may determine that there is no phase-to-phase faultpresent.

This process may be repeated for each phase-to-phase combination. Forexample, the phase A and phase B single-pole switching devices may becontrolled as described above to determine whether a phase-to-phasefault is present. Next, the phase B and phase C single-pole switchingdevices may be controlled as described above to determine whether aphase-to-phase fault is present. Last, the phase A and phase Csingle-pole switching devices may be controlled as described above todetermine whether a phase-to-phase fault is present.

In some embodiments, the above described sniffing process may beutilized to test for phase-to-ground and phase-to-phase faults insystems with any number of phases. For example, in a system that isreceiving single phase electric power, phase-to-ground short testing maybe performed by briefly pulsing the switching device closed and openedand measuring for current. In addition, in a system receiving two phaseelectric power, phase-to-ground testing may be performed for both phasesby briefly pulsing the respective switching devices closed and measuringfor current. Further, phase-to-phase short testing may be performed bybriefly overlapping the closures of the switching devices providing thetwo phase power and analyzing the di/dt slope.

Further, the above described sniffing process using single-poleswitching devices and POW techniques for both phase-to-ground andphase-to-phase short detection may be combined into a thorough detectionsequence that may be executed prior to starting the electric motor 24.One embodiment of a process 584 for the sniffing process is shown inFIG. 57, which is a block diagram of logic for detecting motorconditions. The process 584 may be implemented via computer-readableinstructions stored in a non-transitory article of manufacture (e.g.,the memory 226, 20, 46 and/or other memories) and executed via processor224, 19, 45 and/or other control circuitry. It should be noted that thedepicted sequence of the process 584 is not meant to be limiting, and isfor illustrative purposes. Indeed, any one of the process blocks may berearranged and performed in different order than the depictedembodiment.

In some embodiments, the sequence 584 may begin by testing forphase-to-ground shorts; however, in other embodiments, the sequence 584may begin by testing for phase-to-phase faults. As such, phase A may beanalyzed for a phase-to-ground short by closing the single-poleswitching device 576 at a desired point on the waveform ahead of avoltage zero-crossing, opening the single-pole switching device 576after a few milliseconds, and measuring for current (process block 586).Next, in process block 588, the control and monitoring circuitry 18 mayperform sniffing on phase B to detect whether a phase-to-ground shortexists (process block 588). That is, the single-pole switching device578 may be briefly pulsed closed ahead of a voltage zero-crossing. Then,the single-pole switching device 578 may be opened after a fewmilliseconds, and the current may be measured to determine whethercurrent is flowing to the ground. In process block 590, the control andmonitoring circuitry 18 may perform sniffing on phase C to detectwhether a phase-to-ground short exists (process block 590).

If there is current sensed by the sensors 22 for any one of the phases,a phase-to-ground short may be present, and a user may determine howmuch current is present and decide whether to start the load (e.g.,electric motor 24) or not. If there is no current sensed for any of thephases during the phase-to-ground detection, or the user decides toproceed with starting, the sequence 584 may move to testing forphase-to-phase faults.

To test for phase-to-phase faults, the control and monitoring circuitry18 may utilize sniffing to detect whether there is a phase A to phase Bfault present (process block 592). Additionally, the control andmonitoring circuitry 18 may utilize sniffing to detect whether there isa phase B to phase C fault present (process block 594) and utilizesniffing to detect whether there is a phase A to phase C fault present(process block 596). More specifically, if the di/dt slope indicates aphase-to-phase fault is present, the user may decide to delay startinguntil the condition is remedied. The combined sequence ofphase-to-ground short detecting process blocks 586-590 and thephase-to-phase short detecting process blocks 592-596 may be executed asdesired prior to starting a load (e.g., electric motor 24), such as eachtime before the load starts or on a periodic basis.

As previously mentioned, the benefits of performing the sequence 584, ora combination thereof, may reduce undesirable maintenance conditions ofthe electric motor 24 and its windings and inhibit tripping anyconnected devices through the use of single-pole switching devices andPOW techniques to detect faults using near minimal energy.

In an alternative embodiment, sniffing may be performed two single-poleswitching devices in series to detect phase-to-ground shorts and/orphase-to-phase faults. It should be noted that the single-pole switchingdevices may include the single-pole, single current-carrying pathswitching devices 218. Additionally or alternatively, in someembodiments, single-pole, multiple current-carrying path switchingdevices may be used. The benefits of using two single-pole switchingdevices in series is that it may enable a smaller more accurate timewindow at which electric power is provided to the electric motor 24.FIG. 58A displays an embodiment of a motor system 598 that utilizes twosingle-pole switching devices in series (576 & 600, 578 & 602, 580 &604). More specifically, each pair of switching devices is used tosupply a single phase of electric power from the power source 12 to theelectric motor 24. Additionally, the electric motor 24 may be connectedto ground 584.

As such, FIG. 58A is almost identical to FIG. 56A except for theaddition of the second set of single-pole switching devices 600, 602,and 604. In some embodiments, the second set of single-pole switchingdevices 600, 602, and may form a controllable disconnect switch. Itshould be noted that the disclosed techniques are not limited to twoswitching devices. Indeed, any number of single-pole switching devicesmay be utilized. The two single-pole switching devices in series maydetect faults by briefly overlapping the closures so as to momentarilyallow closing of the circuit. Then, any current that is sensed bysensors 22 may be measured and analyzed by control and monitoringcircuitry 18. For example, a phase-to-ground short may be detected ifany current is detected by the sensors 22 when the circuit is brieflyclosed. Also, a phase-to-phase short may be detected if the di/dt slopeis nearly vertical after syncing the overlapping closure of the twosingle-pole switching devices in series for two phases.

Beginning with phase-to-ground short detection, it may be useful to walkthrough how each pair of single-pole switching devices is utilized.Specifically, with regards to phase A, the control and monitoringcircuitry 18 may utilize POW techniques to pick a desired point on thesinusoidal waveform to close the first single-pole switching device 576in the series ahead of a voltage zero-crossing and another desired pointto close the second single-pole switching device 600 ahead of thevoltage zero-crossing so that both single-pole switching devices'closures overlap for some brief period of time (e.g., a couplemilliseconds) prior to the voltage zero-crossing. Further, the controland monitoring circuitry 18 may also pick a desired point to open thesingle-pole switching devices 576 ahead of the voltage zero-crossing andanother point to open the single-pole switching device 600. Then, thecontrol and monitoring circuitry 18 may pulse the single-pole switchingdevices 576 and 600 closed and opened based upon the desired points. Inthis way, the overlapping closure of both single-pole switching devicesmay be controlled so that the closure is opened before the voltagecrosses zero. Thus, the amount of energy present if there is a fault maybe more precisely controlled when two or more single-pole switchingdevices in series. Also, the amount of time that the switching devices576 and 600 are closed is minimal. As such, it should be noted that theswitching devices may be opened and close anywhere on the sinusoidalwaveforms due to the very brief amount of time that their closuresoverlap.

Accordingly, the control and monitoring circuitry 18 may determinewhether a phase-to-phase fault is present based on the current sensed bythe sensors 22. The above described phase-to-ground short detectionprocess utilizing two single-pole switching devices in series may berepeated for both phase B and phase C using their respective single-poleswitching devices in series (578 & 602, 580 & 604).

The duration of the closure overlap may be better understood withreference to FIG. 58B, which is a timing diagram of closing and openingtwo single-pole switching devices in series. The y-axis represents thevoltage in the coil, and the x-axis represents time in milliseconds.Each solid line and respective dotted line represent a pair ofsingle-pole switching devices in series applying voltage of a singlephase to the electric motor 24. For example, the control and monitoringcircuitry 18 closes the first single-pole switching device 576 at t1 andcloses the second single-pole switching device 600 at t2. Additionally,the control and monitoring circuitry 18 opens the first single-poleswitching device 576 at t3 and opens the second single-pole switchingdevice 600 at t4. Accordingly, since both of the single-pole switchingdevices 576 and 600 are closed between t2 to t3, electric power issupplied to the electric motor 24 between t2 to t3. This timeframe orwindow may be referred to as the “closure overlap.” The closure overlapmay be only one or two milliseconds long. Indeed, closing of thesingle-pole switching devices 576 and 600 may be intended to enable acontrolled pulse of line voltage to be applied that has insufficientenergy to cause an undesirable maintenance condition to the motor and/orits windings.

It is during the closure overlap that the current is measured to detectphase-to-ground shorts. If any current is sensed by the sensors 22,there may be a phase-to-ground short present. In contrast, if no currentis sensed then there may not be a phase-to-ground short present. Asdepicted, the timings of the closing and openings of the other pairs ofsingle-pole switching devices in series for phase B (t5-t8) and phase C(t9-t12) may be similar. More specifically, as depicted, electric poweris applied between t6-t7 and between t1-t11. In other embodiments, thephase-to-ground shorts may be tested in any desirable order. However,two phases should not be tested simultaneously because if the closureoverlaps are synced current will be flowing and it may appear as thoughthere is a phase-to-ground fault when there is not.

To further illustrate the points on the sine wave that the twosingle-pole switching devices in series may close and open, FIG. 59depicts a graphical representation of timing for the motor conditiondetection. The graph shows the voltage sine wave for a single phase ofelectric power over time. For example, the sine wave may represent phaseA and the timings (t1-t4) represent the same single-pole switchingdevice closings and openings shown in FIG. 58B.

As described above, the first single-pole switching device 576 may closeat t1 and open at t3. Additionally, the second single-pole switchingdevice 600 may close at t2 and open at t4. Accordingly, electric powermay be applied to the electric motor 24 between t2 and t3, which asdepicted is slightly before the voltage zero crossing so that the amountof energy available if a fault is present is low. That is, as displayed,the voltage is only applied for a couple of milliseconds while it is lowbefore zero is crossed.

Similarly, the control and monitoring circuitry 18 may also detectphase-to-phase faults utilizing the two single-pole switching devices inseries. For example, in some embodiments, the control and monitoringcircuitry 18 may pulse closed pairs of single-pole switching devices inseries such that electric power is connected for a brief period slightlybefore a phase-to-phase predicted current zero-crossing. This may enablebrief closing of the circuit between phases to apply a small amount ofvoltage for a few milliseconds so that if a fault exists, the fault maybe cleared quickly without causing an undesirable maintenance condition.In addition, the brief closing of the circuit may enable the sensors 22to sense any current that is flowing and the control and monitoringcircuitry 18 to analyze the di/dt slope of the current to determinewhether a phase-to-phase fault is present.

More specifically, the control and monitoring circuitry 18 may utilizethe two single-pole switching devices and POW techniques to detectphase-to-phase faults between phase A to phase B, phase B to phase C,and phase A to phase C, in any order. Taking phase A to phase B shortdetection as an example, the control and monitoring circuitry 18 mayutilize POW techniques to pick points on phase A and phase B where aphase-to-phase voltage maximum (e.g., a predicted current zero-crossing)occurs. Additionally or alternatively, the phase-to-phase current and/orvoltage may be explicitly measured to determine when a current isapproaching between phases. For example, the voltage may be measuredbetween phase A and phase B, between phase B and phase C, and betweenphase A and phase C to determine when to perform the sniffing forphase-to-phase shorts. It is noted that the current conducted may beasymmetrical. As such, it may be possible to determine other desirablepoints to perform sniffing operations, for example, based at least inpart on characteristics of the load.

Next, the control and monitoring circuitry 18 may determine another setof points on the phase A and phase B waveforms that are a few electricaldegrees prior to the predicted current zero-crossings to ensure that alow current is applied when the circuit is closed. Then, the control andmonitoring circuitry 18 may pulse close and open the pairs ofsingle-pole switching devices for both phase A and phase B to createclosure overlaps that coincide (e.g., overlap briefly) between thephases at the determined points before the predicted currentzero-crossing.

That is, the control and monitoring circuitry 18 may pulse close thesingle-pole switching device 576 and then 600 at the desired pointbefore the predicted current zero-crossing to apply voltage for phase A,while at nearly the same time, pulse close the single-pole switchingdevices 578 and then 602 at the desired point before the predictedcurrent zero-crossing to apply voltage for phase B. Thus, both phases'pairs of single-pole switching devices may create closure overlaps thatapply voltage for both phases at the same time in order to detectwhether there is a phase-to-phase fault. Quickly thereafter (e.g.,milliseconds), the single-pole switching device 576 supplying phase Aand the single-pole switching device 578 supplying phase B may be pulsedopen before the predicted current zero-crossing to break the circuit,thereby opening the closure overlap.

As such, utilizing the single-pole switching devices in series betweenphases in this manner may provide the benefit of generating a moreaccurate pulse that is more precise in both amount of current appliedand the duration of current application in relation to the predictedcurrent zero-crossing. As a result, the controlled pulse of line voltageapplied may be insufficient to cause an undesirable maintenancecondition and/or trip connected devices (e.g., feeder circuit breaker)if a short is present. Further, if a short is detected the electricmotor 24 may not be started so that the problem may be remedied anddetriments inhibited.

In some embodiments, the above described sniffing process utilizing twoswitching devices in series may be utilized to test for phase-to-groundand phase-to-phase faults in systems with any number of phases. Forexample, in a system that is receiving single phase electric power,phase-to-ground short testing may be performed by briefly overlappingthe closure of the two switching devices in series and measuring forcurrent. In addition, in a system receiving two phase electric power,phase-to-ground testing may be performed for each individual phase bybriefly overlapping the closures of the switching devices in series forthat particular phase and measuring for current. Further, phase-to-phaseshort testing may be performed for a system receiving two phase power bybriefly overlapping the closures of the switching devices in series forboth phases and analyzing the di/dt slope.

Accordingly, utilizing the sniffing techniques described above mayenable controlling the amount and duration of electric power applied toa motor. As such, potential undesirable maintenance conditions that mayoccur when a fault is present may be reduced and protection circuitrymay not trip if a fault is present. More specifically, in the event of ashort circuit, the fault current may be much smaller than when closingat full voltage, and the very brief pulse may easily clear the faultcurrent. Thus, expensive repairs may be reduced, equipment up time maybe increased, and operator safety may be improved.

Modular System Constructions

There are multiple configurations of devices enabled to meet desiredneeds by leveraging the techniques described herein. Specifically, theelectromechanical single-pole switching devices described above, such asthe single-pole, single current-carrying path switching devices 218,provide modularity that enables highly configurable devices. Further,the mechanical interlock described above enhances device configurabilityby preventing a particular switching device from closing when aninterlocked switching device is closed, which may inhibit shorts. Onesuch modular device that utilizes the techniques described herein is thewye-delta starter described above. Indeed, in the embodiments describedbelow, 5-pole, 6-pole, 8-pole, and 9-pole wye-delta starters are enabledutilizing electromechanical single-pole switching devices (e.g.,single-pole, single current-carrying path switching devices) inconjunction with the mechanical interlock. It should be noted that thenumber of poles may correspond to the number of single-pole switchingdevices utilized in the configuration. In general, using the single-poleswitching devices in the described wye-delta starter embodiments mayresult in devices having a compact size, which may save a user money dueto less hardware utilized and less complex wiring, and a lower thermalfootprint, which may improve ability to package such a device in asmaller electrical enclosure with a smaller factory footprint.

To help illustrate, one embodiment of a polyphase 5-pole wye-deltastarter 374 is shown in FIG. 60. As depicted, the 5-pole wye-deltastarter 374 includes five single-pole switching devices 376, 378, 380,382, and 384, which may be electromechanical single-pole, singlecurrent-carrying path switching devices. Additionally or alternatively,the switching devices 376, 378, 380, 382, and 384 may includesingle-pole, multiple current-carrying path switching devices.Specifically, the 5-pole wye-delta starter 374 includes two wyeswitching devices 376 and 378 and three delta switching devices 380,382, and 384. The switching devices are coupled to three-phase powerfrom three mains lines 392, 394, and 396, and are further coupled tothree motor windings 386, 388, and 390. An advantage provided by usingthe single-pole, single current-carrying path switching devices insteadof switches arranged on a common switch carrier is the number of powerpoles may be reduced (e.g., fewer switching devices). For example, the5-pole wye-delta switching device utilizes two wye switching devices(376 and 378) instead of three.

As depicted, the first delta switching device 380 and the first wyeswitching device 376 are mechanically coupled via a first interlock 608,and the second delta switching device 382 and the second wye switchingdevice 378 are mechanically coupled via a second interlock 610. Itshould be noted that the first interlock 608 and second interlock 610may be the mechanical interlock described above. As such, only one ofthe first delta switching device 380 and the first wye switching device376 may be closed at a time. Similarly, only one of the second deltaswitching device 382 and the second wye switching device 378 may beclosed at a time. In addition, operation of the wye-delta starter 374may be controlled by the control and monitoring circuitry 18.

Additionally, as depicted, the output of first delta switching device380 and the output of first wye switching device 376 are electricallycoupled via a first interconnection 628. Similarly, the output of seconddelta switching device 382 and the output of second wye switching device378 are electrically coupled via a second interconnection 624.Furthermore, the output of third delta switching device 384, the inputof first wye switching device 376, and the input of first deltaswitching device 380 are electrically coupled via a thirdinterconnection 620.

In the operation, the wye-delta starter 374 may receive a signal tostart the motor. Using the techniques above, the wye-delta starter 374may initially execute a wye two-step start and then phase sequentialwye-delta switching. Both processes may include the control andmonitoring circuitry 18 opening and/or closing specified switchingdevices in a sequential order so as to minimize negative torque, currentspikes, and oscillation magnitudes. As such, the wye two-step start maybe initiated by the second wye switching device 378 closing. Thus, afirst phase of electric power (e.g., phase A) is connected from themains line 394 to the motor second winding 388 and a second phase ofelectric power (e.g., phase B) may be connected from the mains line 396to the third winding 390. During the second step of the wye two-stepstart, the second first wye switching device 376 closes and a thirdphase of electric power (e.g., phase C) is connected from the mains line392 to the first winding 386 of the electric motor 24. Thus, when thewye switching devices 376 and 378 are the only switching devices closedin the wye-delta starter 374, the motor is running in a wyeconfiguration.

When initiated, the wye-delta starter 374 may execute the phasesequential wye-delta switching. As such, the switching may begin byopening the first wye switching device 376. As a result of breakingfirst wye switching device 376, the motor windings 388 and 390 are beingsupplied power. Next, the first delta switching device 380 may beclosed, resulting in first winding 386 being connected line 394 to line392. Windings 388 and 390 are still connected line 394 to line 396. As aresult of first delta switching device 380 closing, the windings 386,388, and 390 are receiving three-phase unbalanced power due to the motorrunning in a mixed wye-delta configuration. Then, the second wyeswitching device 378 may be opened as the third step in the phasesequential wye-delta transition. As a result, only motor first winding386 is receiving power and the electric motor 24 is single phasing.Further, the second delta switching device 382 may be closed after theopening of the second wye switching device 378, thereby providing powerto second winding 388 in addition to 386. Last, the third deltaswitching device 384 may be closed in order to complete the deltaconfiguration. Thus, three-phase power may be supplied via lines 392,394, and 396 to the motor windings 386, 388, and 390 in a deltaconfiguration.

As previously discussed, in some embodiments, the 5-pole wye-deltastarter 374 may be implemented with single-pole, single current-carryingpath switching devices 218, as depicted in FIG. 61. More specifically,as depicted, the mains line 394 is electrically coupled to inputterminal 612 of the first delta switching device 380, the mains line 396is electrically coupled to input terminal 614 of the second deltaswitching device 382, and the mains line 392 is electrically coupled toinput terminal 616 of the third delta switching device 384.

Additionally, the output terminal 626 of the first delta switchingdevice 380 and the output terminal of the first wye switching device 376are electrically coupled by the first interconnect 628 (e.g., a firstbus bar). Similarly, the output terminal 632 of the second deltaswitching device 382 and the output terminal 636 of the second wyeswitching device 378 are electrically coupled by the second interconnect634 (e.g., a second bus bar). Furthermore, the input terminal 618 of thefirst wye switching device 376, the input terminal 622 of the second wyeswitching device 378, and the output terminal 624 of the third deltaswitching device 384 are electrically coupled by the third interconnect620 (e.g., a third bus bar).

Thus, the first winding 386 may be electrically coupled to either outputterminal 626, output terminal 630, or the first interconnect 628.Additionally, the second winding 388 may be electrically coupled toeither output terminal 632, output terminal 624, or the secondinterconnect 634. Furthermore, the third winding 390 may be electricallycoupled to either input terminal 618, input terminal 622, or outputterminal 624.

Additionally, as depicted, the first delta switching device 380 and thefirst wye switching device 376 are mechanically coupled by the firstinterlock 608. Similarly, second delta switching device 382 and secondwye switching device 378 are mechanically coupled by the secondinterlock 610. It should be noted that the first interlock 608 andsecond interlock 610 may be the mechanical interlock described above.

In another embodiment, a polyphase 6-pole wye-delta starter 442 isenabled utilizing six switching devices, as shown in FIG. 62. As withthe 5-pole wye-delta starter, the switching devices may beelectromechanical single-pole, single current-carrying path switchingdevices independently operated by the control and monitoring circuitry18. Additionally or alternatively, the switching devices may besingle-pole, multiple current carrying path switching devices. Asdepicted, the configuration of the switching devices is almost identicalas the 5-pole wye-delta starter except another wye switching device isincluded in this embodiment. Indeed, the 6-pole wye-delta starter 442includes six switching devices 444, 446, 448, 450, 452, and 454.Specifically, the 6-pole wye-delta starter 442 includes three wyeswitching devices 444, 446, and 448 and three delta switching devices450, 452, and 454.

The switching devices are coupled to three-phase power from three mainslines 462, 464, and 466, and are further coupled to three motor windings456, 458, and 460. As discussed above, the 6-pole wye-delta starter 442may be controlled by the control and monitoring circuitry 18 to keeptrack of which switching devices open and/or close first during a startand select a different switching device to open and/or close during thenext start. In this way, the control and monitoring circuitry 18 mayevenly distribute the number of switching operations each switchingdevice performs, which may increase the lifespan of the switchingdevices.

As depicted, the first delta switching device 450 and the wye switching444 are coupled via a first interlock 638, the second delta switchingdevice 452 and the second wye switching device 446 are coupled via asecond interlock 640, and the third delta switching device 454 and thethird wye switching device 448 are coupled via a third interlock 642. Itshould be noted that the interlocks 638, 640, and 642 may be themechanical interlocks described above. As such, only one of the firstdelta switching device 450 and the first wye switching device 444 may beclosed at a time, only one of the second delta switching device 452 andthe second wye switching device 446 may be closed at a time, and onlyone of the third delta switching device 454 and the third wye switchingdevice 448 may be closed at a time.

Additionally, as depicted, the output of first delta switching device450 and the output of first wye switching device 444 are electricallycoupled via a first interconnection 660. Similarly, the output of seconddelta switching device 452 and the output of second wye switching device446 are electrically coupled via a second interconnection 666, and theoutput of third delta switching device 454 and the output of third wyeswitching device 448 are electrically coupled via a thirdinterconnection 672. Furthermore, the input of first wye switchingdevice 444, the input of second wye switching device 446, and the inputof third wye switching device 448 are electrically coupled via a fourthinterconnection 665.

The steps in the wye two-step start and the phase sequential wye-deltaswitching using six switching devices are essentially the same as usingfive switching devices, which was described with reference to FIG. 60.However, in the circuit diagram 442 depicted in FIG. 62 there are threewye switching devices (444, 446, and 448), as opposed to two in FIG. 60.Thus, the order in which the wye switching devices are closed in the wyetwo-step start may change, and the order in which the wye switchingdevices are opened in the phase sequential wye-delta switching maychange. In particular, regarding the wye two-step start, in order toprovide current to the windings using three wye switching devices, oneof the steps may close two wye switching devices simultaneously and theother step may close the third switching device. For example, the wyeswitching devices 446 and 448 may close simultaneously to connectwindings 458 and 460 from line 464 to line 466. Then, in the secondstep, the third first wye switching device 444 may close in order tocomplete the wye configuration. If POW techniques are utilized, theseclosures may occur at desired points on the sinusoidal waveforms asdetermined by the control and monitoring circuitry 18.

Once the electric motor 24 is running in wye configuration and thewinding current waveforms have reached steady state, the phasesequential switching to delta may initiate. Alternatively, the phasesequential switching to delta may initiate any point after the motor isset in the wye configuration. As with the phase sequential wye-deltaswitching utilizing a 5-pole wye-delta starter, in one embodiment, thefirst step in the sequence utilizing a 6-pole wye-delta starter mayinclude opening one of the wye switching devices 444. Next, theswitching device 450 may be closed to connect first winding 456 indelta. After switching device 450 closes, the motor is running in amixed wye-delta configuration with first winding 456 in delta andwindings 458 and 460 in wye. Then, the remaining two closed wyeswitching devices 446 and 448 may be opened simultaneously and theelectric motor 24 may be single phasing (e.g., phase A) with only firstwinding 456 connected line 462 to line 464. The switching devices 452and 454 may be closed following the closure of the switching device 450either one after the other or simultaneously. As a result, the windings456, 458, and 460 are receiving three-phase electric power and theelectric motor is running in a delta configuration.

As previously discussed, in some embodiments, the 6-pole wye-deltastarter 442 may be implemented with single-pole, single current-carryingpath switching devices 218, as depicted in FIG. 63. More specifically,as depicted, the mains line 464 is electrically coupled to inputterminal 644 of first delta switching device 450, the mains line 466 iselectrically coupled to input terminal 646 of second delta switchingdevice 452, and the mains line 462 is electrically coupled to inputterminal 648 of third delta switching device 454.

Additionally, the output terminal 658 of first delta switching device450 and the output terminal 662 of the first wye switching device 444are electrically coupled by the first interconnect 660 (e.g., a firstbus bar). Similarly, the output terminal 664 of the second deltaswitching device 452 and the output terminal 668 of the second wyeswitching device 446 are electrically coupled by the second interconnect666 (e.g., a second bus bar), and the output terminal 670 of the thirddelta switching device 454 and the output terminal of the third wyeswitching device 448 are electrically coupled by the third interconnect672 (e.g., a third bus bar. Furthermore, the input terminal 650 of thefirst wye switching device 444, the input terminal 654 of the second wyeswitching device 446, and the input terminal 656 of the third wyeswitching device 448 are electrically coupled by the fourth interconnect665 (e.g., a fourth bus bar).

Thus, the first winding 456 may be electrically coupled to either outputterminal 658, output terminal 662, or the first interconnect 660.Additionally, the second winding 458 may be electrically coupled toeither output terminal 664, output terminal 668, or the secondinterconnect 666. Furthermore, the third winding 460 may be electricallycoupled to either output terminal 670, output terminal 674, or the thirdinterconnect 672.

Additionally, as depicted, the first delta switching device 450 and thefirst wye switching device 444 are mechanically coupled by the firstinterlock 638. Similarly, the second delta switching device 452 and thesecond wye switching device 446 are mechanically coupled by the secondinterlock 640. Furthermore, the third delta switching device 454 and thethird wye switching device 448 are mechanically coupled by the thirdinterlock 642. It should be noted that the interlocks 638, 640, and 642may each be the mechanical interlock described above.

In another embodiment, the polyphase 5-pole wye-delta starter may bemodified to isolate the motor windings by adding three mains linesswitching devices, which results in the polyphase 8-pole wye-deltastarter 676 shown in FIG. 64. As with the 5-pole wye-delta starter, theswitching devices may be electromechanical single-pole, singlecurrent-carrying path switching devices independently operated by thecontrol and monitoring circuitry 18. Additionally or alternatively, theswitching devices may be single-pole, multiple current carrying pathswitching devices. Independent operation enables making/breaking atdifferent times and in different orders. As depicted, the configurationof the switching devices is identical to the 5-pole wye-delta starterexcept for the addition of three mains lines switching devices in the8-pole wye-delta starter embodiment. The 8-pole wye-delta starter 676includes eight switching devices 678, 680, 682, 686, 688, 690, 692, and694.

Specifically, the 8-pole wye-delta starter 676 includes two wyeswitching devices 678 and 680, three delta switching devices 682, 684,and 686, and three mains lines switching devices 688, 690, and 692. Thethree mains lines switching devices 688, 690, and 692 are electricallycoupled to three-phase power from three mains lines 694, 696, and 698and are further coupled to three motor windings 700, 702, and 704 andthe delta switching devices 682, 684, and 686. The delta switchingdevices 682, 684, and 686 are also electrically coupled to the wyeswitching devices 678 and 680 and the windings 700, 702, and 704. Anadvantage of utilizing the mains line switching devices 688, 690, and692 is that they may be utilized as disconnects in order to protect theelectric motor 24 from undesirable maintenance by faulty conditions orthe like. Additionally, utilizing the mains lines switching devices 688,690, and 692 may enable testing condition of the electric motor 24before performing a start. For example, as discussed above,phase-to-ground and phase-to-phase shorts may be tested using the mainslines switching devices. Further, the mains lines switching devices mayact as disconnects in case a short is present or the windings need to beisolated from the mains power.

As depicted, the first delta switching device 682 and the first wyeswitching device 678 are coupled via a first interlock 706, and thesecond delta switching device 684 and the second wye switching device680 are coupled via a second interlock 708. It should be noted that theinterlocks 706 and 708 may be the mechanical interlocks described above.As such, only one of the first delta switching device 682 and the firstwye switching device 678 may be closed at a time, and only one of thesecond delta switching device 684 and the second wye switching device680 may be closed at a time.

Additionally, as depicted, the output of first delta switching device682 and the output of first wye switching device 678 are electricallycoupled via a first interconnection 738. Similarly, the output of thesecond delta switching device 684 and the output of second wye switchingdevice 680 are electrically coupled via a second interconnection 744.Furthermore, the input of the first wye switching device 678, the inputof the second wye switching device 680, and the output of the thirddelta switching device 686 are electrically coupled via a thirdinterconnection 732.

The steps in the wye two-step start and the phase sequential wye-deltaswitching using eight switching devices are essentially the same asusing five switching devices. However, in the circuit diagram 676depicted in FIG. 64 there are three mains lines switching devices (694,696, and 698) that are isolating the windings (700, 702, and 704). Thus,when a signal to start the motor is received by the 8-pole wye-deltastarter, the mains line switching devices (688, 690, and 692) may closeprior to running the wye two-step start and the phase sequentialwye-delta switching. After the mains line switching devices are closed,the wye two-step start and the phase sequential wye-delta switching maybe executed the same as the 5-pole wye-delta starter.

Specifically, the wye two-step start may begin by the second wyeswitching device 680 closing. Thus, windings 702 and 704 may bereceiving power from line 696 to line 698. During the second step of thewye two-step start the first wye switching device 678 closes and a thirdphase of electric power (e.g., phase C) is connected from the mains line694 to the first winding 700 of the electric motor 24. Thus, when thewye switching devices 678 and 680 and the mains line switching devices688, 690, and 692 are the only switching devices in the 8-pole wye-deltastarter 676 that are closed, the motor is running in a wyeconfiguration.

When initiated, the 8-pole wye-delta starter 676 may execute phasesequential wye-delta switching. As such, the transition may begin byopening the first wye switching device 678. As a result of breakingswitching device 678, only motor windings 702 and 704 are being suppliedpower. Next, the first delta switching device 682 may be closed,resulting in first winding 700 being connected line 696 to line 694 indelta. Windings 702 and 704 are still connected line 696 to line 698 inwye. Thus, as a result of the first delta switching device 682 closing,the windings 700, 702, and 704 are receiving three-phase unbalancedpower due to the motor running in a mixed wye-delta configuration. Then,the second wye switching device 680 may be opened as the third step inthe phase sequential wye-delta transition. As a result, only motor firstwinding 700 is receiving power and the electric motor 24 is singlephasing. Further, the second delta switching device 684 may be closedafter the opening of the second wye switching device 680, therebyproviding power to second winding 702 in addition to 700.

The third delta switching device 686 may then be closed in order tocomplete the delta configuration. Thus, three-phase power being may besupplied via lines 694, 696, and 698 to the motor windings 700, 702, and704 in a delta configuration. However, if at any time the control andmonitoring circuitry 18 determines that power needs to be cut off fromthe electric motor 24, the mains line switching devices (688, 690, and692) may be signaled to open one at a time or all at once. If POWtechniques are utilized the openings may be ahead of currentzero-crossings.

In some embodiments, the 8-pole wye-delta starter 676 may be implementedwith single-pole, single current-carrying path switching devices 218, asdepicted in FIG. 65. More specifically, as depicted, the first mainsline 696 is electrically coupled to input terminal 712 of the firstmains line switching device 690, the second mains line 698 iselectrically coupled to input terminal 714 of the second mains lineswitching device 692, and the third mains line 694 is electricallycoupled to input terminal 710 of the third mains line switching device688. The output terminal 716 of the third mains line switching device688 is electrically coupled to the input terminal 718 of the third deltaswitching device 682, the output terminal 720 of the first mains lineswitching device 690 is electrically coupled to the input terminal 722of the first delta switching device 682, and the output terminal 724 ofthe second mains line switching device 692 is electrically coupled tothe input terminal 726 of the second delta switching device 684.

Additionally, the output terminal 736 of first delta switching device682 and the output terminal 740 of the first wye switching device 678are electrically coupled by the first interconnect 738 (e.g., a firstbus bar). Similarly, the output terminal 742 of the second deltaswitching device 684 and the output terminal 746 of the second wyeswitching device 680 are electrically coupled by the second interconnect744 (e.g., a second bus bar). Furthermore, the input terminal 728 of thefirst wye switching device 678, the input terminal 730 of the second wyeswitching device 746, and the output terminal 734 of the third deltaswitching device 686 are electrically coupled by the third interconnect732 (e.g., a third bus bar).

Thus, the first winding 700 may be electrically coupled to either outputterminal 736, output terminal 740, or the first interconnect 738.Additionally, the second winding 702 may be electrically coupled toeither output terminal 742, output terminal 746, or the secondinterconnect 744. Furthermore, the third winding 704 may be electricallycoupled to either output terminal 734, input terminal 728, inputterminal 730, or the third interconnect 732

Additionally, as depicted, the first delta switching device 682 and thefirst wye switching device 678 are mechanically coupled by the firstinterlock 706. Similarly, the second delta switching device 684 and thesecond wye switching device 680 are mechanically coupled by the secondinterlock 702. It should be noted that the interlocks 702 and 706 mayeach be the mechanical interlock described above.

In another embodiment, the polyphase 6-pole wye-delta starter may bemodified to isolate the motor windings by adding three mains lineswitching devices, which results in the polyphase 9-pole wye-deltastarter 748 shown in FIG. 66. As with the 6-pole wye-delta starter, theswitching devices may be electromechanical single-pole, singlecurrent-carrying path switching devices independently operated by thecontrol and monitoring circuitry 18. Additionally or alternatively, theswitching devices may include single-pole, multiple current carryingpath switching devices. Independently operating the switching devicesenables making/breaking at different times and in different orders.Further, the 9-pole wye-delta starter 748 may be enabled with or withoutPOW techniques. As depicted, the configuration of the switching devicesis almost identical as the 6-pole wye-delta starter except for theaddition of three mains line switching devices in the 9-pole wye-deltastarter embodiment. As such, the 9-pole wye-delta starter 748 includesnine switching devices 750, 752, 754, 756, 758, 760, 762, 764, and 766.

Specifically, the 9-pole wye-delta starter 748 includes three wyeswitching devices 750, 752, and 754, three delta switching devices 756,758, and 760, and three mains line switching devices 762, 764, and 766.The three mains line switching devices are electrically coupled tothree-phase power from three mains lines 768, 770, and 772 and arefurther electrically coupled to three motor windings 774, 776, and 778and the delta switching devices 756, 758, and 760. The delta switchingdevices 756, 758, and 760 are also electrically coupled to the wyeswitching devices 750, 752, and 754 and the windings 774, 776, and 778.An advantage of utilizing the mains line switching devices 762, 764, and766, is that they may be utilized as disconnects in order to protect theelectric motor 24 from undesirable maintenance by faulty conditions orthe like. By acting as a gatekeeper to the mains power, the mains lineswitching devices 762, 764, and 766 are able to isolate the windings774, 776, and 778. Further, in some embodiments, the mains lineswitching devices 762, 764, and 766 may be utilized to test forphase-to-ground and phase-to-phase shorts before starting the motor.

As depicted, the first delta switching device 756 and the wye switching750 are coupled via a first interlock 780, the second delta switchingdevice 758 and the second wye switching device 752 are coupled via asecond interlock 782, and the third delta switching device 760 and thethird wye switching device 754 are coupled via a third interlock 784. Itshould be noted that the interlocks 780, 782, and 784 may be themechanical interlocks described above. As such, only one of the firstdelta switching device 756 and the first wye switching device 750 may beclosed at a time, only one of the second delta switching device 758 andthe second wye switching device 752 may be closed at a time, and onlyone of the third delta switching device 760 and the third wye switchingdevice 754 may be closed at a time.

Additionally, as depicted, the output of first delta switching device756 and the output of first wye switching device 750 are electricallycoupled via a first interconnection 826. Similarly, the output of thesecond delta switching device 758 and the output of second wye switchingdevice 752 are electrically coupled via a second interconnection 832,and the output of the third delta switching device 760 and the output ofthe third wye switching device 754 are electrically coupled via a thirdinterconnection 820. Furthermore, the input of the first wye switchingdevice 750, the input of the second wye switching device 752, and theinput of the third wye switching device 754 are electrically coupled viaa fourth interconnection 831.

The steps in the wye two-step start and the phase sequential wye-deltaswitching using nine switching devices are essentially the same as usingsix switching devices. However, in the circuit diagram 748 depicted inFIG. 66 there are three mains line switching devices 762, 764, and 766that are isolating the windings 774, 776, and 778. Thus, before runningthe wye two-step start and the phase sequential wye-delta switching, thecontrol and monitoring circuitry 18 may send signals to close the mainsline switching devices 762, 764, and 766). After the mains lineswitching devices are closed, the wye two-step start and the phasesequential wye-delta switching may be executed the same as the 6-polewye-delta starter.

More specifically, the control and monitoring circuitry 18 may initiatethe wye two-step start by closing the wye switching devices 754 and 752simultaneously to connect windings 776 and 778 from line 770 to line772. Then, in the second step of the wye two-step start, the third firstwye switching device 750 may close in order to complete the wyeconfiguration and provide power to first winding 774.

Once the electric motor 24 is running in wye configuration and thewinding current waveforms have reached steady state, the phasesequential switching to delta may initiate. Alternatively, the phasesequential switching to delta may initiate any point after the motor isset in the wye configuration. In some embodiment, the first step in thesequence may include opening the wye switching devices 750. Thus, onlywindings 776 and 778 are connected and receiving power from line 770 to772. Next, the switching device 756 may be closed to connect firstwinding 774 in delta. After switching device 756 closes, the motor isrunning in a mixed wye-delta configuration with first winding 774 indelta and windings 776 and 778 in wye. Then, the remaining two closedwye switching devices 752 and 754 may be opened simultaneously and theelectric motor 24 may be single phasing (phase A) with only firstwinding 774 connected between line 768 to line 770. As a result, thewindings 774, 776, and 778 may receive three-phase electric power fromlines 768, 770, and 772, and the electric motor 24 is running in a deltaconfiguration.

In some embodiments, the 9-pole wye-delta starter 676 may be implementedwith single-pole, single current-carrying path switching devices 218, asdepicted in FIG. 67. More specifically, as depicted, the first mainsline 770 is electrically coupled to input terminal 788 of the firstmains line switching device 764, the second mains line 772 iselectrically coupled to input terminal 790 of the second mains lineswitching device 766, and the third mains line 768 is electricallycoupled to input terminal 786 of the third mains line switching device762. The output terminal 792 of the third mains line switching device762 is electrically coupled to the input terminal 794 of the third deltaswitching device 760, the output terminal 798 of the first mains lineswitching device 764 is electrically coupled to the input terminal 800of the first delta switching device 756, and the output terminal 804 ofthe second mains line switching device 766 is electrically coupled tothe input terminal 806 of the second delta switching device 758.

Additionally, the output terminal 824 of first delta switching device756 and the output terminal 828 of the first wye switching device 750are electrically coupled by the first interconnect 828 (e.g., a firstbus bar). Similarly, the output terminal 830 of the second deltaswitching device 758 and the output terminal 834 of the second wyeswitching device 752 are electrically coupled by the second interconnect832 (e.g., a second bus bar), and the output terminal 828 of the thirddelta switching device 760 and the output terminal 822 of the third wyeswitching device 754 are electrically coupled by the third interconnect820 (e.g., a third bus bar). Furthermore, the input terminal 814 of thefirst wye switching device 750, the input terminal 816 of the second wyeswitching device 752, and the input terminal 810 of the third wyeswitching device 754 are electrically coupled by the fourth interconnect831 (e.g., a fourth bus bar).

Thus, the first winding 774 may be electrically coupled to either outputterminal 824, output terminal 828, or the first interconnect 826.Additionally, the second winding 776 may be electrically coupled toeither output terminal 830, output terminal 834, or the secondinterconnect 832. Furthermore, the third winding 704 may be electricallycoupled to either output terminal 818, output terminal 822, or the thirdinterconnect 826.

Additionally, as depicted, the first delta switching device 756 and thefirst wye switching device 750 are mechanically coupled by the firstinterlock 780. Similarly, the second delta switching device 758 and thesecond wye switching device 752 are mechanically coupled by the secondinterlock 782. Furthermore, the third delta switching device 760 and thethird wye switching device 754 are mechanically coupled by the thirdinterlock 784. It should be noted that the interlocks 780, 782, and 784may each be the mechanical interlock described above.

An alternative embodiment of the 9-pole wye-delta starter 498 isdepicted in FIG. 68. In this embodiment, instead of utilizing threemains line switching devices, this 9-pole wye-delta starter 498 utilizesthree additional delta switching devices. Thus, the 9-pole wye-deltastarter 498 includes three wye switching devices 500, 502, and 504 andsix delta switching device 506, 508, 510, 512, 514, and 516. It shouldbe noted that the switching devices may be electromechanicalsingle-pole, single current-carrying path switching devicesindependently operated by the control and monitoring circuitry 18.Additionally or alternatively, the switching devices may includesingle-pole, multiple current-carrying path switching devices.Independently operating the switching devices enables making/breaking atdifferent times and in different orders, among other things. Further,the 9-pole wye-delta starter 498 may be enabled with or without POWtechniques. Similar to the previous embodiment of the 9-pole wye-deltastarter 748, the depicted embodiment of the 9-pole wye-delta starter 498isolates the motor windings 836, 838, and 840 from mains lines 842, 844,and 846 by utilizing the three additional delta switching devices 512,514, and 516.

More specifically, the three mains lines 842, 844, and 846 supplythree-phase power and are electrically coupled to the six deltaswitching devices 506, 508, 510, 512, 514, and 516. Three of the deltaswitching devices 512, 514, and 516 are further electrically coupled tothe motor windings 836, 838, and 840, and the other three deltaswitching devices 506, 508, and 510 are further electrically coupled tothe wye switching devices 500, 502, and 504 as well as the three motorwindings 836, 838, and 840. Additionally, an advantage of utilizing thethree additional delta switching devices 512, 514, and 516 to isolatethe electric motor 24, is that they may be utilized as disconnects inorder to protect the electric motor 24 from undesirable maintenance byfaulty conditions or the like. Furthermore, in some embodiments, deltaswitching devices 506, 508, 510, 512, 514, and 516 may be utilized totest for phase-to-ground and phase-to-phase shorts before starting themotor.

In fact, the depicted embodiment may further improve detectingphase-to-phase shorts by reducing duration electrical power is appliedduring testing. More specifically, as depicted, when the first wyeswitching device 500 is open, the first delta switching device 506 and afirst auxiliary delta switching device 512 are coupled in series withthe first winding 836. Similarly, when the second wye switching device502 is open, the second delta switching device 508 and a secondauxiliary delta switching device 514 are coupled in series with thesecond winding 838. Furthermore, when the third wye switching device 504is open, the third delta switching device 510 and a third auxiliarydelta switching device 516 are coupled in series with the third winding840. Thus, the opening/closing of each delta switching device andauxiliary delta switching device may be offset from one another. In thismanner, duration the electric power is applied to the winding may bereduced even less than the minimum duration either of the switchingdevices is closed.

Additionally, as depicted, the first delta switching device 506 and thewye switching 500 are coupled via a first interlock 848, the seconddelta switching device 508 and the second wye switching device 502 arecoupled via a second interlock 850, and the third delta switching device510 and the third wye switching device 504 are coupled via a thirdinterlock 852. It should be noted that the interlocks 848, 850, and 852may be the mechanical interlocks described above. As such, only one ofthe first delta switching device 506 and the first wye switching device500 may be closed at a time, only one of the second delta switchingdevice 508 and the second wye switching device 502 may be closed at atime, and only one of the third delta switching device 510 and the thirdwye switching device 504 may be closed at a time.

Similar to the previously described embodiment of the 9-pole wye-deltastarter 748, the output of first delta switching device 506 and theoutput of first wye switching device 500 are electrically coupled via afirst interconnection 888. Similarly, the output of the second deltaswitching device 508 and the output of second wye switching device 502are electrically coupled via a second interconnection 894, and theoutput of the third delta switching device 510 and the output of thethird wye switching device 504 are electrically coupled via a thirdinterconnection 900. Furthermore, the input of the first wye switchingdevice 500, the input of the second wye switching device 502, and theinput of the third wye switching device 504 are electrically coupled viaa fourth interconnection 901.

Additionally, since the 9-pole wye-delta starter 498 include auxiliarydelta switching devices instead of mains switching devices, the input ofthe first auxiliary delta switching device 512 and the third deltaswitching device 510 are electrically coupled via a fifthinterconnection 862. Similarly, the input of the second auxiliary deltaswitching device 514 and the input of the first delta switching device506 are electrically coupled via a sixth interconnection 864.Furthermore, the input of the third auxiliary switching device 516 andthe input of the second delta switching device 508 are electricallycoupled via a seventh interconnection 868.

The steps in the wye two-step start and the phase sequential wye-deltaswitching using nine switching devices are essentially the same as usingsix switching devices. However, in the depicted circuit diagram 498there are three auxiliary delta switching devices (512, 514, and 516)may isolate the windings (836, 838, and 840). Thus, before running thewye two-step start and the phase sequential wye-delta switching, thecontrol and monitoring circuitry 18 may send signals to close theauxiliary delta switching devices (512, 514, and 516). After theauxiliary delta switching devices are closed, the wye two-step start andthe phase sequential wye-delta switching may be executed the same as the6-pole wye-delta starter as discussed above with reference to the otherembodiment of the 9-pole wye-delta starter FIG. 66.

In some embodiments, the 9-pole wye-delta starter 498 may be implementedwith single-pole, single current-carrying path switching devices 218, asdepicted in FIG. 69. More specifically, the output terminal 886 of firstdelta switching device 506 and the output terminal 884 of the first wyeswitching device 500 are electrically coupled by the first interconnect888 (e.g., a first bus bar). Similarly, the output terminal 892 of thesecond delta switching device 508 and the output terminal 890 of thesecond wye switching device 502 are electrically coupled by the secondinterconnect 894 (e.g., a second bus bar). Furthermore, and the outputterminal 898 of the third delta switching device 510 and the outputterminal 896 of the third wye switching device 504 are electricallycoupled by the third interconnect 900 (e.g., a third bus bar).Furthermore, the input terminal 870 of the first wye switching device500, the input terminal 872 of the second wye switching device 502, andthe input terminal 874 of the third wye switching device 504 areelectrically coupled by the fourth interconnect 901 (e.g., a fourth busbar).

Thus, the first winding 836 may be electrically coupled to either outputterminal 884, output terminal 886, or the first interconnect 888.Additionally, the second winding 838 may be electrically coupled toeither output terminal 890, output terminal 892, or the secondinterconnect 894. Furthermore, the third winding 840 may be electricallycoupled to either output terminal 896, output terminal 898, or the thirdinterconnect 900.

Additionally, as depicted, the input terminal 854 of the first auxiliarydelta switching device 512 and the input terminal of the third deltaswitching device 512 are electrically coupled by the fifthinterconnection 862 (e.g., a fifth bus bar). Similarly, the inputterminal 856 of second auxiliary delta switching device 514 and theinput terminal of the first delta switching device 506 are electricallycoupled by the sixth interconnection 864 (e.g., a sixth bus bar).Furthermore, the input terminal 858 of the third auxiliary deltaswitching device 516 and the input terminal 866 of the second deltaswitching device 508 are electrically coupled by the seventhinterconnection 868 (e.g., a seventh bus bar).

Thus, the first mains line 842 may be electrically coupled to eitherinput terminal 854, input terminal 860, or the fifth interconnection862. Additionally, the second mains line 844 may be electrically coupledto either input terminal 856, input terminal 858, or the sixthinterconnection 864. Furthermore, the third mains line 846 may beelectrically coupled to either input terminal 858, input terminal 866,or seventh interconnection 868.

Furthermore, as depicted, the first delta switching device 506 and thefirst wye switching device 500 are mechanically coupled by the firstinterlock 848. Similarly, the second delta switching device 508 and thesecond wye switching device 502 are mechanically coupled by the secondinterlock 850. Furthermore, the third delta switching device 510 and thethird wye switching device 504 are mechanically coupled by the thirdinterlock 852. It should be noted that the interlocks 848, 850, and 852may each be the mechanical interlock described above.

As evidenced by the varying configurations of a 9-pole wye-deltastarter, one of ordinary skill the art should appreciate that themodularity provided be single pole, single current carrying pathswitching device 218 enables varying advantages, such as adjustingconfiguration based on size constraints. For example, one arrangementmay be desirable over the other depending on various factors (e.g., theenclosure constraints, location of the electric motor 24, etc.), andwhile either may achieve similar functions.

In addition to the wye-delta starters, other devices may also utilizethe techniques described herein, such as an electric motor reverser, atwo speed motor, or a motor drive bypass. To help illustrate, oneembodiment of an electric motor reverser 902, is shown in FIG. 70. Asdepicted, the reverser 902 includes a first forward switching device904, a second forward switching device 906, a first reverse switchingdevice 908, a second reverse switching device 910, and a commonswitching device 912. More specifically, as depicted, the input of thefirst forward switching device 904 and the input of the second reverseswitching device 910 are electrically coupled by a first interconnect934. Similarly, the input of the first reverse switching device 908 andthe input of the second forward switching device 906 are electricallycoupled by a second interconnect 940. Furthermore, the output of thefirst forward switching device 904 and the output of the first reverseswitching device 908 are electrically coupled by a third interconnect946. Similarly, the output of the second reverse switching device 910and the output of the second forward switching device 906 areelectrically coupled by a fourth interconnect 952.

Additionally, as depicted, the first forward switching device 904 andthe first reverse switching device 908 are coupled via a first interlock914, and the second forward switching device 906 and the second reverseswitching device 910 are coupled via a second interlock 916. In otherwords, only one of the first forward switching device 904 and the firstreverse switching device 908 may be closed at a time. Similarly, onlyone of the second forward switching device 906 and the second reverseswitching device 910 may be closed at a time. Additionally, operation ofthe reverser 902 may generally be controlled by the control andmonitoring circuitry 18.

In the depicted embodiment, when the first forward switching device 904is closed, a first phase of electric power (e.g., phase A) is connectedfrom the first mains line 918 to the first motor terminal 920 of theelectric motor 24; when the second forward switching device 906 isclosed, a second phase of electric power (e.g., phase B) is connectedfrom the second mains line 922 to the second motor terminal 924 of theelectric motor 24; and when the common switching device 912 is closed, athird phase of electric power (e.g., phase C) is connected from thethird mains line 926 to the third motor terminal 928 of the electricmotor 24. Thus, when the first forward switching device 904, the secondforward switching device 906, and the common switching device 912 areclosed, the motor rotates in a forward direction (e.g., firstdirection).

Generally, a reverser may change the rotational direction of an electricmotor 24 (e.g., from forward to reverse) by disconnected electric powerand reconnecting the electric power with two of the phases switched.Accordingly, in some embodiments, to reverse the electric motor, thecontrol and monitoring circuitry 18 may break the first forwardswitching device 904, the second forward switching device 906, and thecommon switching device 912. For example, the second forward switchingdevice 906 may be opened based upon a first current zero-crossing, andthe first forward switching device 904 and the common switching device912 may be opened based upon a subsequent zero-crossing. Additionally oralternatively, POW techniques are not used and the switching devices maybe opened after a brief delay.

Then, the first reverse switching device 908, second reverse switchingdevice 910, and the common switching device 912 may be closed. Forexample, the second reverse switching device 910 and the commonswitching device 912 may be closed based upon a first predicted currentzero-crossing (e.g., maximum line-to-line voltage), and the firstreverse switching device 908 may be closed based upon a subsequentpredicted current zero-crossing. More specifically, when the firstreverse switching device 908 is closed, the second phase of electricpower (e.g., phase B) is connected from the second mains line 922 to thefirst motor terminal 920; when the second reverse switching device 910is closed, the first phase of electric power (e.g., phase A) isconnected from the first mains line 918 to the second motor terminal924, and when the common switching device 912 is closed, the third phaseof electric power (e.g., phase C) is connected from the third mains line926 to the third motor terminal 928. Thus, when the first reverseswitching device 908, the second reverse switching device 910, and thecommon switching device 912 are closed, the motor rotates in the reversedirection (e.g., opposite direction).

In some embodiments, since the common switching device 912 simplydisconnects and reconnects the same phase of electric power (e.g., phaseC) to the same motor terminal (e.g., third motor terminal) of theelectric motor, the common switching device 912 may remain closed duringthe reverse operation. In such embodiments, even though the commonswitching device 912 remains closed, the common switching device 912 maystill be included to disconnect the third phase of electric power fromthe electric motor 24. Additionally or alternatively, in otherembodiments, the common switching device 912 may be removed entirely.

In either embodiment where the one phase of electric power remainsconnected during the reverse operation, the control and monitoringcircuitry 18 may break the first forward switching device 904 and thesecond forward switching device 906. For example, the second forwardswitching device 906 may be opened based upon a first currentzero-crossing and the first forward switching device 904 may be openedbased upon a subsequent current zero-crossing. Then the control andmonitoring circuitry may make the first reverse switching device 908 andthe second reverse switching device 910. For example, the secondswitching device 910 may be closed based upon a first predicted currentzero-crossing and the first reverse switching device 908 may be closedbased upon a subsequent predicted current zero-crossing.

In some of the embodiments of the reverser 902 described above, eachswitching device may be controlled independently. For example, asdescribed above, the first forward switching device 904 and the secondforward switching device 906 may make/break at different times and indifferent orders. Accordingly, to improve the control over eachswitching device, the reverser 902 may be implemented with single-poleswitching devices (e.g., single-pole, single current-carrying pathswitching devices 218), as depicted in FIG. 71.

To implement the reverser 902, as depicted, the input terminal 930 ofthe first forward switching device 904 and the input terminal 932 of thesecond reverse switching device 910 are electrically coupled via thefirst interconnection 934 (e.g., a first bus bar). Thus, the first mainsline 918 may be connected to either input terminal 930, input terminal932, or the first interconnection 934. Additionally, as depicted, theinput terminal 936 of the first reverse switching device 908 and theinput terminal 938 of the second forward switching device 906 areelectrically coupled via the second interconnection 940 (e.g., a secondbus bar). Thus, the second mains line 922 may be connected to eitherinput terminal 936 or 938.

On the output side, the output terminal 942 of the first forwardswitching device 904 and the output terminal 944 of the first reverseswitching device 908 are electrically coupled via the third interconnect946 (e.g., a third bus bar). Thus, the first motor terminal 920 may beconnected to either output terminal 942, output terminal 944, or thethird interconnect 946. Additionally, as depicted, the output terminal948 of the second reverse switching device 910 and the output terminal950 of the second forward switching device 906 are electrically coupledvia the fourth interconnect 952 (e.g., a fourth bus bar). Thus, thesecond motor terminal 924 may be connected to either output terminal948, output terminal 950, or the fourth interconnect 952.

Furthermore, in the depicted embodiment, the input terminal 954 of thecommon switching device 912 may be connected to the third mains line 926and the output terminal 956 of the common switching device 912 may beconnected to the third motor terminal 928. As described above, thereverser 902 may be implemented with or without the common switchingdevice 912. Thus, the modular nature of the single-pole path switchingdevices 218 (e.g., single-pole, single current-carrying path switchingdevices) enables each implementation to be individually configured. Forexample, in a first configuration, the reverser 902 may include thecommon switching device 912, but in a second configuration, the reverser902 may exclude the common switching device 912. Even though the commonswitching device 912 is excluded in the second configuration, theconfiguration of the remaining switching devices (e.g., 904-910) willlargely remain the same.

Similar to the motor reverser 902, a two speed motor may be implementedusing five single pole, single current carrying path switching devices218. As described above, a motor drive bypass may also utilize thetechniques described herein. To help illustrate, one embodiment of amotor drive bypass 958 that may be utilized to bypass the motor drive960, is shown in FIG. 72. In some embodiments, the motor drive 960 maybe a soft starter, across the line starter, variable frequency drive, orthe like.

As depicted, the motor drive bypass 958 includes a first mainsdisconnect 962, a second mains disconnect 964, a third mains disconnect966, a first input disconnect 968, a second input disconnect 970, athird input disconnect 972, a first bypass switching device 974, asecond bypass switching device 976, a third bypass switching device 978,a first output disconnect 980, a second output disconnect 982, and athird output disconnect 984 (e.g., switching devices). Morespecifically, the output of the first mains disconnect 962, the input ofthe first input disconnect 968, and the input of the first bypassswitching device 974 are electrically coupled by a first interconnect986. Similarly, the output of the second mains disconnect 964, the inputof the second input disconnect 970, and the input of the second bypassswitching device 976 are electrically coupled by a second interconnect996. Furthermore, the output of the third mains disconnect 926, theinput of the third input disconnect 972, and the input of the thirdbypass switching device 978 are electrically coupled by a thirdinterconnect 1006.

Additionally, as depicted, the output of the first bypass switchingdevice 974 and the output of the first output disconnect 980 areelectrically coupled by a fourth interconnect 992. Similarly, the outputof the second bypass switching device 976 and the output of the secondoutput disconnect 982 are electrically coupled by a fifth interconnect1002. Furthermore, the output of the third bypass switching device 978and the output of the third output disconnect 984 are electricallycoupled by a sixth interconnect 1012.

Operation of the motor drive bypass 958 may generally be controlled bythe control and monitoring circuitry 18. Generally, when the disconnectsare closed and the bypass switching devices 974-978 are open, the motordrive 960 receives three-phase electric power and outputs three-phaseelectric power. For example, in the depicted embodiment, the r input ofthe motor drive 960 receives a first phase of electric power (e.g.,phase A) from the first mains line 918, the s input of the motor drive960 receives a second phase of electric power (e.g., phase B) from thesecond mains line 922, and the t input of the motor drive 960 receives athird phase of electric power (e.g., phase C) from the third mains line926. Additionally, the u output of the motor drive 960 outputs the firstphase of electric power to the first motor terminal 920, the v output ofthe motor drive 960 outputs the second phase of electric power to thesecond motor terminal 924, and the w output of the motor drive 960outputs the third phase of electric power to the third motor terminal928. It should be noted that other motor or load controlling devices maybe used.

Accordingly, control and monitoring circuitry 18 may utilize the mainsdisconnects 962-966 to selectively connect and disconnect electric powerfrom both the motor driver 960 and the electric motor 24. Morespecifically, when the first mains disconnect 962 is opened, the firstphase of electric power is disconnected; when the second mainsdisconnect 964 is opened, the second phase of electric power isdisconnected; and when the third mains disconnect 966 is opened, thethird phase of electric power is disconnected. For example, the secondmains disconnect 964 may be opened based upon a first currentzero-crossing, and the first mains disconnect 962 and the third mainsdisconnect 966 may be opened based upon a subsequent currentzero-crossing. However, in some embodiments, POW techniques may not beused and the switching devices may be closed and opened in any desiredmanner. In some embodiments, the mains disconnects 962-966 may beoptionally excluded because the electric power may be selectivelyconnected and disconnected from both the motor drive 960 and theelectric motor 24, for example, by the input disconnects 966-970.

Instead of completely disconnecting electric power to the electric motor24, at times, it may be desirable to disconnect electric power from themotor drive 960 but continue supplying power to the electric motor 24,for example, to reduce power consumption or to perform maintenance onthe motor drive 960. Accordingly, the bypass switching devices 974-978may be closed to bypass the motor drive 960.

More specifically, control and monitoring circuitry 18 may open theinput disconnects 968-972 and the output disconnects 980-984 todisconnect electric power from the motor drive 960. In some embodiments,the input disconnects 968-972 may be opened substantiallysimultaneously. In other embodiments, the input disconnects 968-972 maybe opened using point-on-wave (POW) techniques. For example, the secondinput disconnect 970 may be opened based upon a first currentzero-crossing, and the first input disconnect 968 and the third inputdisconnect 972 may be opened based upon a subsequent currentzero-crossing. Similarly, in some embodiments, the output disconnects980-984 may be opened substantially simultaneously. In otherembodiments, the output disconnects 980-984 may be opened using POWtechniques. For example, the second output disconnect 982 may be openedbased upon a first current zero-crossing, and the first outputdisconnect 980 and the third output disconnect 984 may be opened basedupon a subsequent current zero-crossing.

To reduce the possibility of electric power being back fed into themotor drive 960 via the outputs, the bypass switching devices 974-978may be closed after the output disconnects 980-984 are opened. In someembodiments, the bypass switching devices 974-978 may be closedsubstantially simultaneously. In other embodiments, the bypass switchingdevices 974-978 may be closed using POW techniques. For example, thefirst bypass switching device 974 and the third bypass switching device978 may close based upon a first predicted current zero-crossing, andthe second bypass switching device 976 may close based upon a subsequentpredicted current zero-crossing.

Once the bypass switching device 974-978 make, the first phase ofelectric power may be supplied from the first mains lines 918 throughthe first bypass switching device 974 to the first motor terminal 920,the second phase of electric power may be supplied from the second mainslines 922 through the second bypass switching device 976 to the secondmotor terminal 924, and the third phase of electric power may besupplied from the third mains line 926 through the third bypassswitching device 978 to the third motor terminal 928. In other words,the drive bypass 958 enables the electric motor 24 to continue actuatingeven after the motor drive 960 is bypassed. This may prove especiallyuseful for high reliability systems, such as a waste management system.

In some of the embodiments of the drive bypass 958 described above, eachswitching device may be controlled independently. For example, asdescribed above, the first bypass switching device 974 and the secondbypass switching device 976 may make/break at different times and indifferent orders. Accordingly, to improve the control over eachswitching device, the drive bypass 958 may be implemented withsingle-pole switching devices 218 (e.g., single-pole, singlecurrent-carrying path switching devices), as depicted in FIG. 73.

To implement the drive bypass 958, as depicted, the output terminal ofthe first mains disconnect 962 is electrically coupled to the inputterminal of the first input disconnect 968 and the input terminal of thefirst bypass switching device 974 via the first interconnect 986 (e.g.,a first bus bar). Thus, the first mains line 918 may be connected to theinput terminal 988 of the first mains disconnect 962 and the outputterminal 990 of the first input disconnect 968 may be connected to the rinput of the motor drive 960.

Similarly, as depicted, the output terminal of the second mainsdisconnect 964 is electrically coupled to the input terminal of thesecond input disconnect 970 and the input terminal of the second bypassswitching device 976 via the second interconnect (e.g., a second busbar). Thus, the second mains line 922 may be connected to the inputterminal 998 of the second mains disconnect 964 and the output terminal1000 of the second input disconnect 970 may be connected to the s inputof the motor drive 960.

Furthermore, as depicted, the output terminal of the third mainsdisconnect 966 is electrically coupled to the input terminal of thethird input disconnect 972 and the input terminal of the third bypassswitching device 978 via the third interconnect 1006 (e.g., a third busbar). Thus, the third mains line 926 may be connected to the inputterminal 1008 of the third mains disconnect 966 and the output terminal1010 of the third input disconnect 970 may be connected to the t inputof the motor drive 960.

As depicted, the output terminal of the first output disconnect 980 andthe output terminal of the first bypass switching device 974 areelectrically coupled by the fourth interconnect 992 (e.g., a fourth busbar). Similarly, the output terminal of the second output disconnect 982and the output terminal of the second bypass switching device 974 areelectrically coupled by the fifth interconnect 1002 (e.g., a fifth busbar). Additionally, the output terminal of the third output disconnect984 and the output terminal of the third bypass switching device 978 areelectrically coupled by the sixth interconnect 1012 (e.g., a sixth busbar).

Thus, the input terminal 994 of the first output disconnect 980 may beconnected to the u output of the motor drive 960, the input terminal1004 of the second output disconnect 982, may be connected to the voutput of the motor drive 960, and the input terminal 1014 of the thirdoutput disconnect 984 may be connected to the w output of the motordrive 960. Moreover, the first motor terminal 920 may be electricallycoupled to the output terminal of the first output disconnect 980, theoutput terminal of the first bypass switching device 974, or the fourthinterconnect 992. Similarly, the second motor terminal 924 may beelectrically coupled to the output terminal of the second outputdisconnect 982, the output terminal of the second bypass switchingdevice 976, or the fifth interconnect 1002. Furthermore, the third motorterminal 928 may be electrically coupled to the output terminal of thethird output disconnect 984, the output terminal of the third bypassswitching device 978, or the sixth interconnect 1012.

Additionally, as described above, the drive bypass 958 may beimplemented with or without the main line disconnects 962-966. Thus, themodular nature of the single-pole switching devices 218 (e.g.,single-pole, single current-carrying path switching devices) enableseach implementation to be individually configured. For example, in afirst configuration, the drive bypass 958 may include the main linedisconnects 962-966, but in a second configuration, the drive bypass 958may exclude the main line disconnects 962-966. In fact, in someembodiments, excluding the main line disconnects 962-966 may enable thebypass switching devices 974-978 and the output disconnects 980-984 tobe adjacent with a mechanical interlock placed therebetween. Moreover,by adjusting the size and length of the bus bars may enable theplacement of each switching device 218 to be individually determined.

Starting with FIG. 74, the single-pole switching devices 1014, 1016, and1018 may function as a three pole contactor using direct on line (DOL)operation to connect and disconnect three phase power from the powersource 12 to the load 14. It should be appreciated that theconfiguration depicted in FIG. 74 may function as a three pole contactorusing DOL with or without POW techniques. As described above, variousbenefits may be achieved using POW techniques, such as reducing inrushcurrent when closing and inhibiting arcing when opening.

In some embodiments, each of the single-pole switching devices 1014,1016, and 1018 may be independently controllable and can be operated inany desired sequence. For example, each single-pole switching device maybe opened/closed at the same time. In another example, two of thesingle-pole switching devices 1014 and 1016 may be opened/closed at afirst time and a third single-pole switching device 1018 may be closedat a second time after the first time. In yet another example, one ofthe single-pole switching devices 1014 may be opened/closed at firsttime and then the other two single-pole switching devices 1016 and 1018may be closed at a second time after the first time.

To this end, using single-pole switching devices enables taking turnsbetween the order with which the single-pole switching devices areopened/closed to enable reducing wear and tear on the switching devices.For example, the single-pole switching device that breaks first duringone operation may be controlled to break last in a subsequent operation.Indeed, certain schemes may be used, such as round robin, when selectingthe order in which to break and/or make the single-pole switchingdevices.

FIG. 75 depicts the three single-pole switching devices 1014, 1016, and1018 with an added fourth single-pole switching device 1020 used as aneutral or ground. The single-pole switching devices 1014, 1016, 1018,and 1020 may supply power from the power source 12 to the load 14.Essentially, in some embodiments, the depicted configuration may beoperated in the same way as the configuration in FIG. 74 as a standardthree pole contactor using DOL operation with or without POW techniquesbut accounting for the fourth single-pole switching device 1020 toconnect and disconnect to ground as desired. Additionally, in someembodiments, the four single-pole switching devices 1014, 1016, 1018,and 1020 may be independently controlled to connect and disconnect inany sequence to function as a soft starter for a motor (e.g., usingwye-delta) with or without POW techniques, as described above.

The modular configurations of single-pole switching devices describedabove may be achieved through various connection arrangements as shownin FIGS. 76-80. As may be appreciated, the design of the power terminalson the single-pole switching devices may be modified as desired toenable the switching devices to be connected in multiple ways that mayreduce wiring complexity and configuration size.

For example, FIG. 76 illustrates two identical single-pole switchingdevices 1022 and 1024 arranged next to one another. The single-poleswitching device 1022 and 1024 each includes two power terminals locatedat the same height protruding from two opposite sides of the switchingdevices 1022 and 1024. That is, the single-pole switching device 1022includes a first power terminal 1026 and a second power terminal 1028 atthe same height and the single-pole switching device 1024 includes afirst power terminal 1030 and a second power terminal 1032 at the sameheight. As depicted, the second power terminal 1028 of the single-poleswitching device 1022 is aligned with the first power terminal 1030 ofthe single-pole switching device 1024. The power terminals 1028 and 1030may be connected using a bus bar 1034 with connecting pins 1036 that areinserted through apertures 1038 in the bus bar 1034 and the powerterminals 1028 and 1030.

In another embodiment, the power terminals of the single-pole switchingdevices may be located at different heights on the two opposing sides,as shown in FIG. 77. As illustrated, a single-pole switching device 1040includes a first power terminal 1042 located at a lower height on oneside than a second power terminal 1044 on an opposing side of thesingle-pole switching device 1040. Using an identical single-poleswitching device 1046 with power terminals located at the same heights,the two switching devices 1040 and 1046 may be connected by overlappingthe power terminals. As shown, a first power terminal 1048 of thesingle-pole switching device 1046 aligns underneath the second powerterminal 1044 of the single-pole switching device 1040, and the powerterminals 1044 and 1048 are connected via a connecting pin 1036. Assuch, the depicted configuration may obviate use of a bus bar to connectthe single-pole switching devices 1040 and 1046.

In another embodiment, the power terminals of the single-pole switchingdevices may be configured to fit together, as shown in FIG. 78. Asillustrated, a single-pole switching device 1050 includes a first powerterminal 1052 with a groove on the bottom of the terminal on one sideand a second power terminal 1054 with a groove on the top of theterminal that matches the groove of the first power terminal 1052 on theopposing side. Using an identical single-pole switching device 1056 withpower terminals including the grooves, the two switching devices 1050and 1056 may be connected by mating the power terminals together. Asshown, a first power terminal 1058 of the single-pole switching device1056 fits with the second power terminal 1054 of the single-poleswitching device 1050 by mating grooves, and the power terminals 1054and 1058 are connected via a single connecting pin 1036. As such, thedepicted configuration may obviate use of a bus bar to connect thesingle-pole switching devices 1050 and 1056.

FIGS. 79 and 80 depict top views of various configurations of more thantwo single-pole switching devices that reduce the amount of wiringneeded to connect the switching devices. For example, FIG. 79illustrates single-pole switching devices 1060, 1062, and 1064 thatinclude power terminals at varying heights so the power terminals mayoverlap one another. That is, power terminal 1066 of switching device1060 is highest, power terminal 1068 of switching device 1062 is at anintermediate height, and power terminal 1070 is at a lowest height.Accordingly, the power terminals may be stacked on top of one anotherand connected via a single connecting pin 1036. As may be appreciated,single-pole switching devices may be arranged to fit within the physicalconstraints of certain housings and may do so by reducing wiring throughdirect connections via power terminals with a single connector pin 1036.

Additionally, FIG. 80 illustrates single-pole switching devices 1072,1074, and 1076 that include power terminals 1078, 1080, and 1082 locatedat the same heights. As described above, a bus bar may be used toconnect power terminals that do not overlap. For example, in thedepicted embodiment, the three power terminals 1078, 1080, and 1082 areconnected via a “T” bus bar 1084 that aligns with apertures 1038 andsecured with connecting pins 1036. Using the above configurations toconnect the single-pole switching devices may provide the benefit ofreducing wiring complexity when arranging certain motor starters.

Provided System Improvements

Moreover, the techniques described herein may facilitate improvedoperation of one or more components in the system 10. In someembodiments, sniffing techniques may be used to facilitate controllingtemperature of a load 14, particularly when the load 14 is not inoperation. For example, control circuitry 18 may instruct single poleswitching devices (e.g., 576, 578, or 580) to periodically conductcurrent through windings in an electric motor 24, thereby heating thewindings. In some embodiments, heating the windings may facilitatesubsequent startup of the motor 24, particularly in cold environments.

To help illustrate, one embodiment of a process 1100 for maintainingtemperature in an electric motor is described in FIG. 81. Generally,process 1100 includes ceasing operation of a load (process block 1102)and determining whether desirable to heat the load (decision block1104). When desirable to heat the load, the process 1100 furtherincludes supplying a first phase and a second phase of electric power(process block 1106), supplying the first phase and a third phase ofelectric power (process block 1108), and supplying the second phase andthe third phase of electric power (process block 1110). The process 1100may be implemented via computer-readable instructions stored in anon-transitory article of manufacture (e.g., the memory 226, 20, 46and/or other memories) and executed via processor 224, 19, 45 and/orother control circuitry.

Accordingly, control circuitry 18 may instruct an electric motor 24 tocease operation (process block 1102). In some embodiments, the controlcircuitry 18 may cease operation of the electric motor 24 by instructingone or more switching devices (e.g., single pole switching devices 576,578, and 580) to open, thereby disconnecting electric power from themotor 24.

The control circuitry 18 may then determine whether it is desirable toheat the electric motor 24 (decision block 1104). In some embodiments,the control circuitry 18 may determine temperature of the electric motor24 via a temperature sensor. In such embodiments, the control circuitry18 may determine that it is desirable to heat the electric motor 24 whenthe temperature of the motor 24 reaches a threshold. Additionally oralternatively, the control circuitry 18 may periodically determine thatit is desirable to heat the electric motor, for example, based on atimer.

When not desirable to heat the electric motor, control circuitry 18 maycontinue waiting until heating is desired (arrow 1112). In someembodiments, the control circuitry 18 may periodically poll thetemperature sensors to determine whether temperature has reached thethreshold.

On the other hand, when heating is desirable, the control circuitry 18may instruct the one or more switching devices to connect a first phase(e.g., phase A) and a second phase (e.g., phase B) of electric power toa first winding in the motor 24 for the short duration (process block1106). For example, in some embodiments the control circuitry 18 mayinstruct the first single pole switching device 576 and the secondsingle pole switching device 578 to close for a short duration (e.g.,sniff) at a first time. In this manner, the first winding may be heateddue to conduction of current.

Additionally, the control circuitry 18 may instruct the one or moreswitching devices to connect the first phase (e.g., phase A) and a thirdphase (e.g., phase C) of electric power to a second winding in the motor24 for the short duration (process block 1108). For example, in someembodiments, the control circuitry 18 may instruct the first single poleswitching device 576 and the third single pole switching device 580 toclose for a short duration (e.g., sniff) at a second time. In thismanner, the second winding may be heated due to conduction of current.

Furthermore, the control circuitry 18 may instruct the one or moreswitching devices to connect the second phase (e.g., phase B) and thethird phase (e.g., phase C) of electric power to a third winding in themotor 24 for the short duration (process block 1110). For example, insome embodiments, the control circuitry 18 may instruct the secondsingle pole switching device 578 and the third single pole switchingdevice 580 to close for a short duration (e.g., sniff) at a third time.In this manner, the third winding may be heated due to conduction ofcurrent.

As described above, supplying two phases of electric power when themotor 24 is stationary may be insufficient to begin rotation of themotor 24. As such, the heating of the windings may be performed whilemaintaining the motor 24 stationary (e.g., non-operational).Additionally, in some embodiments, heating of the electric motor 24 maybe coordinated with testing for phase-to-ground faults and/orphase-to-phase faults. Accordingly, the control circuitry 18 mayinstruct each pair of the single pole switching device 576, 578, and 580to close based at least in part on a predicted current-zero crossing,thereby reducing impact of any potential faults.

Moreover, even when the load 14 is in operation (e.g., electric motor 24is rotating), the temperature of the load 14 may be controlled toimprove operation. For example, when an electric motor 24 is connectedin a partial wye, a partial delta, or a mixed wye-delta configuration,the electric power supplied to each of the windings may vary. As such,the temperature of each winding may differ based at least in part on theamount of conducted electric power. Thus, to facilitate maintainingapproximately equal temperature between the windings, a wye-deltastarter may periodically rotate which windings are connected in whatconfiguration, particularly remaining in a configuration for an extendedperiod.

For example, in a configuration where the wye-delta starter onlyconnects one winding in a delta configuration (e.g., a partial deltaconfiguration described in FIG. G), the wye-delta starter mayperiodically change which winding is connected in the deltaconfiguration. More specifically, the wye-delta starter may periodicallyrotate between connecting the first winding 386 in the deltaconfiguration, connecting the second winding 388 in the deltaconfiguration, and connecting the third winding 390 in the deltaconfiguration. In this manner, by connecting each winding forapproximately the same duration in the delta configuration, thetemperature of the windings may be maintained approximately equal. Oneof ordinary skill should appreciate that such a rotation between thewindings may also be applicable to other partial delta configuration,partial wye configurations, and mixed wye delta configurations.

In addition to improving operation of a load 14, the techniquesdescribed herein may also facilitate improving operation of theswitching devices. More specifically, oxidation may build up oncontactor pads of the switching devices due to contactor contaminationor environmental conditions, such as dust. Accordingly, controlledarcing may be used to clean the contactor pads by burning off oxidation,thereby improving performance and/or lifespan of the switching device.

To help illustrate, one embodiment of a process 1114 for cleaningcontactor pads of a switching device is described in FIG. 82. Generally,the process 1114 includes making a switching device (process block 1116)and determining when desirable to break the switching device (decisionblock 1118). When desired to break the switching device, the processincludes determine whether desirable to clean the switching device(decision block 1120), breaking based on a current zero-crossing whennot desirable to clean the switching device (process block 1122), andcreating an arc when breaking when desirable to clean the switchingdevice (process block 1124). The process 1114 may be implemented viacomputer-readable instructions stored in a non-transitory article ofmanufacture (e.g., the memory 226, 20, 46 and/or other memories) andexecuted via processor 224, 19, 45 and/or other control circuitry.

Accordingly, control circuitry 18 may instruct a switching device tomake, thereby connecting electric power to a load 14 (process block1116). The control circuitry 18 may then determine whether it isdesirable to break the switching device (process block 1118). In someembodiments, the control circuitry 18 may determine that it is desirableto break when desirable to disconnect electric power from the load 14.If not desirable to break, the control circuitry 18 may instruct theswitching device to remain closed and wait until desirable to break(arrow 1126).

On the other hand, when desirable to break, the control circuitry 18 maydetermine whether it is desirable to clean the switching device(decision block 1120). In some embodiments, the control circuitry 18 maydetermine that is desirable to clean the switching device after a setnumber of breaks, for example, every twentieth break. Additionally oralternatively, the control circuitry 18 may determine that it isdesirable to clean based on duration the switching device has been inoperation and/or duration the switching device has been closed.

When not desirable to clean, the control circuitry 18 may instruct theswitching device to break based at least in part on a currentzero-crossing of the conducted electric power (process block 1122). Insome embodiments, the control circuitry 18 may instruct the switchingdevice to break slightly before or at the current zero-crossing, therebyreducing the likelihood and/or magnitude of any arcing. As describedabove, it may be desirable to miss the mark short of the currentzero-crossing and open when the current is going downward on a halfcycle to the current zero-cross, as opposed to missing the mark afterthe current zero-crossing.

On the other when desirable to clean, the control circuitry 18 mayinstruct the switching device to break such that an arc is created asthe contactor pads open (process block 1124). In this manner, the heatproduced by the arcing may burn off any oxidation on the contactor pads,thereby cleaning the switching device. As described above, the magnitudeof arcing may be directly based on where on the current waveform theswitching device breaks. More specifically, the farther the break isfrom a subsequent current zero-crossing the larger the magnitude ofproduced arcing. As such, in some embodiments, the control circuitry 18may determine when to break based on a desired amount of arcing. Forexample, when the switching device has not been cleaned for a longerduration, the control circuitry 18 may determine that greater amount ofcleaning is desirable and break farther from the subsequent current-zerocrossing.

Additionally, in some instances, arcing may cause atoms from onecontactor pad to transfer to the other contactor pad. Thus, in someembodiments, the control circuitry 18 may also determine when to breakthe switching device based on direction desirable to transfer atoms. Infact, in some embodiments, the control system 18 may break the switchingdevice such that the contact pads take turns being the anode and thecathode. In this manner, it may be possible to retain relatively evennumber of atoms on each contactor pad.

74 illustrates an embodiment where three single-pole switching devices1014, 1016, and 1018 are used to connect and disconnect three phasepower and FIG. 75 illustrates an embodiment where four single-poleswitching devices 1014, 1016, 1018, and 1020 are used to connect anddisconnect three phase power plus a neural (e.g., ground).

While only certain features of the disclosure have been illustrated anddescribed herein, many modifications and changes will occur to thoseskilled in the art. It is, therefore, to be understood that the appendedclaims are intended to cover all such modifications and changes as fallwithin the true spirit of the disclosure.

The invention claimed is:
 1. A method comprising: detecting whether aphase-to-ground short is present in a first winding of a motor bybriefly connecting a first phase of electric power to the motor slightlybefore a voltage zero-crossing by the first phase of electric power;detecting whether a phase-to-ground short is present in a second windingof a motor by briefly connecting a second phase of electric power to themotor slightly before a voltage zero-crossing by the second phase ofelectric power; and detecting whether a phase-to-ground short is presentin a third winding of a motor drive by briefly connecting a third phaseof electric power to the motor slightly before a voltage zero-crossingby the third phase of electric power.
 2. The method of claim 1,comprising: detecting whether a phase-to-phase fault is present bybriefly connecting the first phase and the second phase to the motorslightly before a phase-to-phase current zero-crossing; detectingwhether a phase-to-phase fault is present by briefly connecting thesecond phase and the third phase slightly before a phase-to-phasecurrent zero-crossing; and detecting whether a phase-to-phase fault ispresent by briefly connecting the first phase and the third phaseslightly before a phase-to-phase current zero-crossing.
 3. The method ofclaim 2, wherein detecting whether a phase-to-phase fault is presentcomprises: monitoring current that flows when two of the first phase,the second phase, and the third phase are connected to the motor; anddetermining that a phase-to-phase short is present when the current israpidly increasing or that a phase-to-phase open circuit is present whenthe current is zero.
 4. The method of claim 2, wherein connecting thefirst phase and the second phase to the motor comprises: pulsing a firstswitching device closed to connect the first phase to the motor; andpulsing a second switching device close to connect the second phase tothe motor.
 5. The method of claim 1, wherein detecting whether aphase-to-ground short is present comprises: monitoring current thatflows when one of the first phase, the second phase, and the third phaseis connected to the motor; and determining that a phase-to-ground shortis present when the current is not zero.
 6. The method of claim 1,wherein connecting the first phase to the motor comprises pulsing afirst switching device closed.
 7. The method of claim 1, whereinconnecting the first phase to the motor comprises: pulsing a firstswitching device closed at a first time; and pulsing a second switchingdevice closed at a second time, wherein the first switching device andthe second switching device are connected in series.
 8. The method ofclaim 1, wherein the first phase is connected to the motor a durationbetween one to two milliseconds, two to three milliseconds, three tofour milliseconds, or four to five milliseconds.
 9. A switchgear system,comprising: a first switching device configured to selectively connectand disconnect a first phase of electric power to a first winding of amotor; a second switching device configured to selectively connect anddisconnect a second phase of electric power to a second winding of themotor; a third switching device configured to selectively connect anddisconnect a third phase of electric power to a third winding of themotor; and a control circuitry configured to: instruct the firstswitching device to briefly connect the first phase of electric power tothe motor slightly before a voltage zero-crossing by the first phase todetect whether a phase-to-ground short is present in the first winding;instruct the second switching device to briefly connect the second phaseof electric power to the motor slightly before a voltage zero-crossingby the second phase to detect whether a phase-to-ground short is presentin the second winding; and instruct the third switching device tobriefly connect the third phase of electric power to the motor slightlybefore a voltage zero-crossing by the third phase to detect whether aphase-to-ground short is present in the third winding.
 10. Theswitchgear system of claim 9, wherein the control circuitry isconfigured to: instruct the first switching device and the secondswitching device to briefly connect the first phase and the second phaseto detect whether a first phase-to-phase fault is present in the motor;instruct the first switching device and the third switching device tobriefly connect the first phase and the third phase to detect whether asecond phase-to-phase fault is present in the motor; and instruct thesecond switching device and the third switching device to brieflyconnect the second phase and the third phase to detect whether a thirdphase-to-phase fault is present in the motor.
 11. The switchgear systemof claim 10, wherein: the first switching device and the secondswitching device are configured to connect electric power to the motorslightly before a phase-to-phase current zero-crossing between the firstphase and the second phase; the first switching device and the thirdswitching device are configured to connect electric power to the motorslightly before a phase-to-phase current zero-crossing between the firstphase and the third phase; and the second switching device and the thirdswitching device are configured to connect electric power to the motorslightly before a phase-to-phase current zero-crossing between thesecond phase and the third phase.
 12. The switchgear system of claim 10,wherein the first switching device, the second switching device, and thethird switching device are single pole, single current carrying pathswitching devices.
 13. The switchgear system of claim 9, wherein thecontrol circuitry is configured to instruct the first switching device,the second switching device, and the third switching device to connectelectric power to the motor when a fault is not detected in the motor.14. The switchgear system of claim 13, wherein the control circuitry isconfigured to: instruct the first switching device and the thirdswitching device to connect electric power to the motor at aphase-to-phase current zero-crossing between the first phase and thethird phase; and subsequently instruct the second switching device toconnect the second phase of electric power to the motor.
 15. Aswitchgear system, comprising: a first switching device; and a secondswitching device coupled in series with the first switching device,wherein the first switching device and the second switching device areconfigured to briefly supply a first phase of electric power to a firstwinding of a motor by: closing the first switching device at a firsttime; closing the second switching device at a second time; opening thefirst switching device at a third time; and opening the second switchingdevice at a fourth time such that the first phase of electric power issupplied to the first winding between the second time and the third timeto determine whether fault is present in the motor; the second time andthe third time are slightly before a voltage zero-crossing by the firstphase.
 16. The switchgear system of claim 15, wherein supplying thefirst phase of electric power between the second time and the third timeis used to detect whether a phase-to-ground short is present in thefirst winding.
 17. The switchgear system of claim 15, comprising: athird switching device; and a fourth switching device coupled in serieswith the third switching device, wherein the third switching device andthe fourth switching device are configured to briefly supply a secondphase of electric power to a second winding of the motor by: closing thethird switching device at the first time; closing the fourth switchingdevice at the second time; opening the third switching device at thethird time; and opening the fourth switching device at the fourth timesuch that the second phase of electric power is supplied to the firstwinding between the second time and the third time to determine whetherfault is present in the motor.
 18. The switchgear system of claim 17,wherein between the second time and the third time is slightly before aphase-to-phase current zero-crossing between the first phase and thesecond phase.
 19. The switchgear system of claim 18, wherein supplyingthe first phase and the second phase between the second time and thethird time is used to detect whether a phase-to-phase short is presentin the motor.